Determination of moisture in rubber stoppers_ effect of Karl Fischer oven temperatures
162-170
55, 2001 PDA J Pharm Sci and Tech
Zeren Wang, Brenda A. Frankel and William J. Lambert
Fischer Oven Temperatures
Determination of Moisture in Rubber Stoppers: Effect of Karl
162 PDA Journal of Pharmaceutical Science & Technology
ABSTRACT: Moisture released from rubber stoppers of pharmaceutical products may adversely affect prod-
uct quality during storage. The objective of the current study was to identify an appropriate method to quantify free moisture in processed stoppers. The moisture content in stoppers is commonly determined by the Karl Fischer (KF) method. However, for the FM257/2 stoppers from Helvoet, our results suggest that the KF assay results are always lower than that from the gravimetric method and increase with the KF oven temperatures used. The systematic study presented in this manuscript shows that, although moisture results vary with respect to KF oven temperatures, reproducible results are obtained at fixed temperatures. There-fore, the observed variation can not be explained by the release of volatile chemicals from this rubber-affecting KF reagents. Furthermore, by extrapolating moisture results obtained with different thicknesses of rubber slabs to zero thickness, it was found that the diffusion barrier is also not a major source for the variation. It is hypothesized that the moisture in rubber stoppers can be free or bound. The KF method measures both free and bound moisture. As higher KF oven temperatures are used, more bound moisture is released and determined by the KF method. By deducting the bound moisture (measured by the KF method for samples dried at 100oC for one week) from the sample moisture, the amount of free moisture (which is releasable) can be estimated. A KF oven temperature at 250oC is recommended based on the accuracy and precision of the results. This method was validated by showing consistency with the gravimetric method for stoppers undergoing desorption at 25oC and 0% relative humidity (equilibrated with P 2O 5). An example is also presented to show the application of this method.
RESEARCH ARTICLE
Determination of Moisture in Rubber Stoppers: Effect of Karl Fischer Oven Temperatures
Zeren Wang*, Brenda A. Frankel, and William J. Lambert Eisai Inc., Research Triangle Park, North Carolina , USA
* Author to whom correspondence should be addressed:Novartis Pharmaceuticals Corporation, Pharmaceutical and Analytical Development, 59 Route 10, Bldg. 401, East Honover, NJ. E-mail: zeren.wang@https://www.sodocs.net/doc/3716895613.html,
Introduction
Rubber stoppers are widely used as container closures in parenteral products to provide a critical barrier to microbes, moisture and oxygen. These stoppers are often made from natural or synthetic rubber materials.Before a stopper is used for a parenteral product, it may be washed and steam sterilized. These processes, espe-cially the process of steam sterilization, increase the moisture content of the rubber stopper. For freeze-dried and hygroscopic parenteral products, the sorbed mois-ture can be released from stopper and then transferred to the drug product during storage (1,2). Therefore, dry-ing is an essential process to remove excessive mois-ture in stoppers. A critical question is how dry is ac-ceptable. Since the difference in the weight of the stop-pers and the freeze dried prodct is significant, a small (such as 0.1%) amount of free (or releasable) moisture in rubber stoppers can cause a significant increase (such as a few percent) of moisture content in drug prod-ucts. Controversial results have been reported in lit-erature regarding this question. Corveleyn et al. (2)have shown that autoclaved stoppers can still con-tain around 0.3% moisture after being dried at 100oC for 24 hours. When they used these stoppers for a freeze-dried product with a 200 mg cake weight, they found no significant changes (0.5% or less) in the mois-ture content of products after storage for about a year.However, if the amount of moisture (0.3%) in the stop-pers was free moisture or releasable, it could have caused a 4% increase in moisture content in the drug product. Apparently, the total moisture content in rubber stoppers may significantly overestimate the impact in the product.
How does one determine the free moisture of a rubber stopper? Currently, the method suggested by the Inter-national Organization for Standardization (ISO) (3) applies the KF method to directly measure the mois-ture content of rubber stoppers. The ISO method uses a heating oven set at 140oC to drive off moisture from rubber, and the moisture is then subsequently measured by the KF method. One KF coulometric titrator manu-facture suggests using 150oC as the oven temperature for rubber material (4). KF methods with higher KF oven settings have also been reported (2). One issue related to this method is the fact that different moisture contents will be obtained when the KF oven is set at different temperatures (5). A second method used for the evaluation of the moisture content of stoppers after a drying process is the gravimetric method (2). This method is based on the assumption that the weight change (loss) of stoppers during a drying process is the result of moisture release. However, volatile chemicals may be released during drying at elevated temperatures. Thus, the weight loss of a stopper may not directly re-flect the loss of moisture. Furthermore, the gravimetric method can not report the absolute moisture content of a stopper, but rather, the change of moisture content during a specific process.
Another reported approach involves measuring the amounts of moisture transferred to a product during stor-age (1,2). This method often takes several months to obtain meaningful results. In addition, the hygroscop-icity of the product will affect the results.
The purpose of the present study was to develop a method to determine the free moisture in Helvoet FM257/2 stoppers after steam sterilization and heat drying. Parameters such as the KF oven temperature and sample size for the method were investigated.
Materials and Methods
Stoppers –The stoppers (FM257/2, part number V9032, Helvoet Pharma Inc., Pennsauken, NJ) used in the present study were 20 mm diameter lyophilization 3-leg stoppers, weighing about 2.5 g per stopper. These are bromobutyl rubber stoppers coated with fluorinated polymer (Omniflex).
To examine whether the Omniflex coating on the out-side of stoppers has a possible contribution to diffu-sion barrier during the moisture analysis by the KF method, moisture distributions inside autoclaved stop-pers and dried stoppers with, and without, the Omniflex coating were compared and found to be consistent with each other. Thus, the coating can be considered as hav-ing no effect on the KF moisture analysis.
Autoclaving/Drying – For the lab scale autoclave pro-cess, a Falcon 30 autoclave (LTE Scientific Ltd., Greenfield, United Kingdom) was used. The autoclave was maintained at 121oC for the time specified in the legends for figures and tables. The stoppers were then dried in a convection heat oven (Mechanical Convec-tion Oven, Model 625, Precision Scientific, Chicago, IL) at 100oC.
For the pilot plant scale autoclave process, a Getinge PACS20000 autoclave oven (Castle, Inc, Lakewood, NJ) was used. These stoppers were sealed in autoclave bags. The stoppers were then dried in autoclave bags in a Des-patch Dry Heat Oven CWC2-95 (Despatch Industries, Inc, Minneapolis, MN) at 100oC.
KF Moisture Analysis – The moisture content of stop-pers was determined by the KF method using a Karl Fischer Coulometer (Model DL37, Mettler-Toledo, Inc, Columbus, OH) equipped with a heating oven (Model DO337, Mettler-Toledo, Inc, Columbus, OH) purged with dry N
2
at 300 mL/minute. Different oven tempera-tures were examined in the study. The KF titration was stopped at an endpoint of 0.1 μg/sec.
Sample Preparation for the KF Moisture Analysis –Two sample preparation methods were used in this study. For the first method, stoppers were cut into small pieces of approximately 50 mg per piece. For the second method, only the top flange of a stopper was used. It was sliced by a sharp razor blade to square shaped slabs of approximately 0.4 mm in thickness and 6 mm in length on each side. Moisture analysis was performed within one hour after stoppers were cut to minimize moisture absorption or desorption.
For samples used to determine moisture distribution inside the stopper, slabs were sliced layer by layer from surface to inside from the top flange of a stopper. The thickness (average) of slabs was calculated based on the weight, density, and area of samples.
Vol. 55, No. 3, May/June 2001 163
164 PDA Journal of Pharmaceutical Science & Technology
Results and Discussion
The Effect of KF Oven Temperature – Table 1 lists the moisture contents of a set of stopper samples which had been exposed to air at 40oC and 75% relative hu-midity (RH) for four days. The KF method with an oven set at 150oC was first used to monitor the change of moisture content during this storage condition. This KF oven temperature was suggested by the KF coulo-metric titrator manufacture (4), and is close to the oven temperature suggested by ISO (3). The stoppers were cut into small pieces before the KF analysis. To vali-date the KF result, the weight difference of the stop-pers before and after storage was also determined. The weight change was assumed to be only the result of moisture absorption. However, as seen in Table 1, the absorbed moisture amount determined by the KF method (with the KF oven at 150oC), 0.31%, did not match the gravimetric result, 0.47%. Further experi-ments showed that, even with increasing the KF oven temperature, the KF results still did not match the gravimetric method. The results from the KF method were consistently lower than from the gravimetric method.
In addition to the discrepancy results between the KF method and the gravimetric method, it was also found that the stopper moisture content analyzed by the KF method increased with the KF oven temperature (Fig-ure 1). Several possible reasons were investigated to explain this finding. The first possibility was that deg-radation of the rubber occurred during the KF analy-
sis, leading to the release of water either as a reaction product or some other volatile giving a false positive result. The second possibility was that a moisture dif-fusion barrier exists inside the rubber stoppers which decreases with increasing KF oven temperature. Thus,more moisture diffuses out from stoppers during the KF measurement time period at higher KF oven tempera-ture. The third possibility was that some portion of mois-ture is bound to hydrophilic rubber formulation com-ponents and as the KF oven temperature was increased,more bound moisture was released.
If degradation of the rubber material occurred during the KF measurement, the results would presumably show a large variation. In addition, as the KF oven tem-perature increased, degradation would be more signifi-cant and a larger variation of the moisture analysis re-sults should be observed. However, Table 2 shows that the KF analysis of autoclaved stoppers generated a simi-lar relative standard deviation (RSD) for each KF oven temperature used. Furthermore, Figure 2 illustrates the results from another experiment in which the moisture content of rubber stoppers was determined first at a lower KF oven temperature in the range of 150 to 300oC,and then at 300oC again. The total moisture content measured from two measurements is consistent for four different conditions. Therefore, these results suggest that degradation was not responsible for the differ-ence of moisture results obtained at different KF oven temperatures.
Table 1: Moisture Contents of Rubber Stoppers After Storage at 40oC and 75% RH for Four Days
*Since all results were obtained from the same set of stoppers, the weight change is the same and repeated in the table.
Moisture Content after Storage
(%, by KF)0.560.630.721.05
Moisture Content before Storage (%, by KF)0.250.380.460.66
KF Oven Temp. (oC)150200250300
H 20Uptake (%, by KF)0.310.250.260.40
H 20Uptake* (%, by weight)0.47
0.470.470.47
Figure 1: Moisture analysis of stoppers (cut to small pieces) obtained by the KF method with the KF Oven at four different temperatures.
Vol. 55, No. 3, May/June 2001 165
24 hours (previous work in our lab has shown that the moisture content was homogenous inside the stoppers after this treatment). The slabs with different thickness were then assessed by the KF method. The total weights of the slabs were kept about the same (i.e., more slab pieces were used for thinner slabs than the thicker slabs). The results in Figure 3 suggest that a tempera-ture-dependent diffusion barrier exists but is not significant because, although the thickness of the slabs does slightly affect the results, the difference was significant even as the thickness approaches zero.Furthermore, the similarity of the slopes in Figure 3at different KF oven temperatures is also consistent with this suggestion.
As the first two possibilities (degradation of rubber and moisture diffusion barrier) were considered as not pri-mary causes, we focused on the third hypothesis. That is, some portion of moisture is bound to hydrophilic ingredients of rubber material, and can only be freed at high temperatures. Published results (1,2,5) have sug-gested that not all moisture is free during drying. The presence of hydrophilic ingredients in rubber materials has been discussed (6,7), and it has been found that dif-
Table 2: Moisture Contents of Rubber Stoppers (autoclaved at 121oC for 30 minutes in a lab autoclave)Measured by the KF Method at Different KF Oven Temperatures
2nd Assay
0.600.700.721.15
1st Assay 0.590.600.811.06
KF Oven Temp. (oC)150200250300
3rd Assay 0.490.590.610.96
Average 0.560.630.721.05
RSD 11.09.413.89.1
Moisture Content (%)
Figure 2: Moisture analysis of stoppers (sliced slabs) measured initially at a lower temperature and then at 300oC
If moisture analysis variation at different KF oven tem-peratures was caused by a diffusion barrier, then mois-ture results should be inversely proportional to slab thickness and should converge at zero thickness to a single value regardless of KF oven temperature. To test this hypothesis, stoppers were first dried at 100oC for
ferent rubber materials retain different amounts of bound moisture (5). Rubber stoppers are known to con-tain several hydrophilic ingredients (8). Therefore, it is possible that the moisture bound to different hydro-philic ingredients is freed at different temperatures. As the KF oven temperature increases, more moisture is freed from the rubber stopper and detected by the KF coulometric titrator. All the results presented so far are consistent with this hypothesis.
As mentioned in previous paragraphs, the diffusion bar-rier does have a small effect on the KF measurement. As shown in Figure 3, the KF results are slightly lower in thicker samples. This means that some moisture is trapped inside the sample and is not able to be freed before the KF titration was stopped. Increasing the KF oven temperature will decrease the diffusion barrier and therefore improves the accuracy of the KF results. How-ever, at high KF oven temperatures, the KF results con-sist of high percentages of moisture bound at the tem-perature of interest (such as ambient temperatures) but only releasable at high KF oven temperatures. The er-ror of KF results will be amplified when the amount of free moisture is determined (see later sections for de-termination of free moisture). Thus, the precision of the results for free moisture will be compromised at high KF oven temperatures. Our experience suggests that 250oC is preferred for the KF oven temperature at which both accuracy and precision is balanced. The KF analyses for experiments discussed in following sec-tions were all performed with a KF oven set at https://www.sodocs.net/doc/3716895613.html,parison of the Moisture Analysis Results Between the Gravimetric Method and the KF Method – When a stopper absorbs moisture, its weight should increase proportionally. Therefore, the weight change of a stop-per should reflect the amount of moisture absorbed or released, as long as the stopper is not exposed to high temperatures which may volatilize other compounds (5). In fact, monitoring weight changes of rubber stoppers during the process of absorption or desorption of mois-ture has been widely used for the calculation of mois-ture content changes (2,6,7,9).
As mentioned in the previous section, Table 1 compares the results of moisture uptake during an autoclave pro-cess measured by the KF method and the gravimetric method. The results from the KF method were always below that from the gravimetric method. This observa-tion may be explained by the third hypothesis discussed above. Some portion of the moisture absorbed during autoclaving was tightly bound to hydrophilic ingredi-ents in the rubber material. Therefore, only the portion that is free or releasable at each KF oven temperature could be determined by the KF method. The gravimet-ric method reflects the total moisture uptake, which in-cludes both free and bound moisture. Table 1 also shows that the measured moisture uptake is more or less con-sistent in the temperature region from 150 to 250oC for the KF oven. However, a significant increase was observed at 300oC. This suggests that more absorbed moisture can be freed at 300oC than that at the lower temperatures. Figure 4 shows the results of moisture content deter-mined by the KF method and the gravimetric method for rubber stoppers which were subjected to a desorp-tion process (equilibrated with P
2
O
5
). Consistent results were observed between the two methods. This consis-tency was expected since during the desorption process at the room temperature, the weight loss can only be due to moisture loss. Furthermore, the amount of bound moisture is the same between the stoppers before and after the desorption process and is cancelled out during the measurement. Since each result in Figure 4 is from two KF measurements, before and after a desorption process, the error of results is also doubled. The RSD (of data points on Figure 4 away from the theoretical line with a slope of 1) is about 20%, which is twice the RSD of KF measurements, as shown in Table 2.
Effect of the Ratio of Sample Surface Area to Volume – The ratio of sample surface area to volume
Figure 3: Actual moisture results of rubber slabs
with different thicknesses when measured by the KF
166 PDA Journal of Pharmaceutical Science & Technology
Vol. 55, No. 3, May/June 2001 167
is inversely proportional to the thickness of a sample.Figure 3 shows that the thickness of rubber slabs is not responsible for the difference of the moisture results determined at different KF oven temperatures. How-ever, Figure 3 also indicates that thickness does affect the moisture results to some extent. For example, when 250oC was chosen as the KF oven temperature, the moisture result obtained from a 1.5 mm thick slab was about 20% lower than from a 0.3 mm thick slab. There-fore, for sliced slab samples, a thickness of around 0.4 mm was used. The estimated error was less than 10% by extrapolating the results on Figure 3 to zero millimeter thickness.
For sample stoppers cut into small pieces, the ratio of surface area to volume was directly proportional to the number of pieces per stopper. Figure 5 illustrates the effect of this ratio (surface area to volume) in the form of the number of pieces per stopper on the KF mois-ture results when a whole rubber stopper was cut into small pieces. The stoppers were autoclaved at 121oC for 16 minutes and then dried for 16 hours. When 50pieces or more per stopper (or less than 100 mg per piece) were used, the differences are small. In a pre-liminary experiment, it was also found that the mois-ture content of stoppers that were cut to larger pieces (such as seven pieces per stopper) was significantly lower than the moisture content of the same stoppers
that were cut to smaller pieces. Therefore, in all stud-ies reported here, except when otherwise noted, mois-ture analyses of whole stoppers were performed with stoppers cut to 50 pieces or more per stopper (50 mg per piece or smaller).
Figures 3 and 5 suggest that diffusion barriers may be an issue if the sample size is large. Furthermore, the diffusion barrier is more significant at low temperatures.Thus, the conclusion (that is, 50 pieces per stopper may be enough) drawn from Figure 5 is only correct if 250oC
Figure 4: Comparison of moisture results of stoppers from the KF method (at 250oC KF oven temperature)and the gravimetric method
The stoppers were first stored at 40oC with 75% RH for 11days and then stored at 25oC with 0% RH for varying times.The line is theoretical based on a slope of 1.
Moisture Results by Gravimetric Method (%)
M o i s t u r e R e s u l t s b y t h e K F M e t h o d s (%)
0.00
0.20
0.40
0.60
0.80
0.8
0.6
0.4
0.20.0
0.40
0.30
0.32
0.34
0.36
0.38
100
20
40
60
80
Figure 5: Moisture levels of rubber stoppers determined by the KF method with sample stoppers cut to differ-ent numbers of pieces
Figure 6: Moisture distribution inside autoclaved rubber stoppers (at 121oC for 30 minutes in a lab autoclave oven)
0.02.5
0.5
1.0
1.5
2.0
0.0
1.5
1.00.5Depth Inside Stopper (mm)
% o f M o i s t u r e
168 PDA Journal of Pharmaceutical Science & Technology
or greater is used as the KF oven temperature. If a low KF oven temperature such as 150oC is used, the sample size may need to be smaller than 50 mg per piece (or more than 50 pieces per stopper).
Determination of the Amount of Releasable Moisture – Figure 6 demonstrates the moisture distri-bution inside autoclaved stoppers. Figure 7 shows the moisture distribution inside autoclaved stoppers after drying at 100oC for one day, one week, three weeks,and four weeks. The moisture distribution of autoclaved stoppers does not change after drying at 100oC for one week. This suggests that one week was sufficient to completely remove the moisture that can be freed at 100oC. Although the amount of moisture was still mea-surable by subsequent KF determinations after drying at 100oC for up to four weeks, this additional moisture represented moisture that could not be freed at 100oC.
Therefore, the results in Figure 7 helped establish a way
Depth Inside Stoppers (mm)
% o f M o i s t u r e
Figure 7: Moisture distribution inside rubber stoppers that were autoclaved at 121oC for 30 minutes and then dried at 100oC for different times
to determine the amount of bound moisture inside rub-ber stoppers: dry stoppers at 100oC for one week or longer and then measure moisture content by the KF method. The moisture content determined by this method represents the amount of bound moisture that can not be freed at 100oC, but may be freed at high tempera-tures. The amount of free moisture at 100oC is calculated by subtracting the amount of bound mois-ture (determined after drying at 100oC for one week)from the amount of moisture determined before the dry-ing (at 100oC for one week). The measurement of the amount of free moisture at 100oC can be finished in rea-sonably short time (about one week). Practically, only the free moisture can jeopardize pharmaceutical products.It has also been shown from this study that the portion of free moisture changes with environmental tempera-ture. As the temperature goes higher, more moisture inside rubber stoppers can be freed. It would be ideal if
the amount of free moisture at 25oC or ambient tem-peratures can be easily measured. Several literature examples (1,2,5) have shown that the determination of the amount of moisture transferred from stoppers to products or desorbed from stoppers at 25oC and 40oC can be assessed. However, these studies require months to complete, which makes the method impractical for developing a stopper drying process.
It can be reasonably assumed that the actual amount of free moisture at ambient temperatures is lower than the free moisture at 100oC. Therefore, the current method overestimates the amount of free moisture (or transfer-able to products) during storage. Consequently, the stopper drying process developed based on the free moisture results at 100oC is a conservative approach. However, the results in the following section demon-strate that this approach is reasonable. On the other hand, several months were saved by measuring the amount of free moisture at 100oC instead of the amount of free moisture at ambient temperatures.
The stoppers used for the determination of bound mois-ture should be pre-treated exactly the same way as the stoppers used for determination of free moisture because the amount of bound moisture will differ with pre-treatment (such as autoclaving or drying). One approach is to withdraw two sets of samples and then dry one set of the samples at 100oC for one week. The difference in moisture contents measured by the KF method from these two sample sets is the amount of free moisture at 100oC. It should be noted that the ap-proach and conditions described in this article may not be universally applied (without any modification) to other stoppers with different rubber formulations. In addition, the time used to remove all free moisture at 100oC may be different for different stoppers and dif-ferent oven designs. However, the concept presented here may be applicable for developing a KF method to determine the amount of free moisture in differ-ent stoppers.
Application of the Method – During the development of a stopper drying process, the acceptable amount of free moisture in stoppers depends on the cake weight, the stopper weight and the acceptable moisture content in the lyophilized product (or cake). Table 3 lists the corresponding limits of free moisture contents for dif-ferent combinations of stopper sizes and product sizes assuming an upper limit of 0.5% moisture increase in the product during storage. This table considered the fact that the product contact surface area of a stopper is Table 3: Limits of Moisture Content for a Hypothetical Product with a 0.5% Moisture Increase Limit
Stopper Weight
(g)
2.5
2.5
2.5
2.5
0.6
0.6
0.6
0.6
Cake Weight
(g)
0.4
0.2
0.1
0.05
0.4
0.2
0.1
0.05
Moisture Limit
for Stopper (%)
0.13
0.07
0.03
0.02
0.56
0.28
0.14
0.07
Table 4: Moisture Analysis Results of Autoclaved and Dried Stoppers by the KF Method
Stopper Process Conditions
Autoclave for 16 minutes, vacuum dry for 30 minutes
Autoclave for 16 minutes, vacuum dry for 30 minutes, oven dry at 100oC for 16 hours Autoclave for 16 minutes, vacuum dry for 30 minutes, oven dry at 100oC for one week Moisture Content (%)
± SD (n = 3)
0.52 ± 0.02
0.34 ± 0.02
0.31 ± 0.02
Releasable Moisture
(%)
0.21
0.03
___
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170 PDA Journal of Pharmaceutical Science & Technology
the stopper that weighs 2.5 g per stopper to be used for any product that weighs 100 mg or higher, based on the limit set in Table 3. Note that the drying temperature and time were confirmed with the stopper vendor. No adverse effect should be caused by this drying cycle.
Acknowledgements
The authors wish to thank Mr. Charles Reichel for his great technical support in some of the studies, and Mr.Eddie Ballance, Mrs. Kim Weathers, Mr. Bill Baskerville,and Mr. Allen Grobin for the work performed in the pilot plant. Suggestions to the manuscript offered by Dr. Lana Burrell are gratefully acknowledged.
about 60% of its total surface area, and only the mois-ture from the product contact surface can be transferred to a product cake. It is shown in the table that a tight moisture limit is needed for a large stopper that is used for a small product cake. For a small cake weight, such as 50 mg, a small stopper, such as 13 mm size, may be favorable, in order to minimize moisture transfer. How-ever, if higher moisture contents in a product cake are allowed, the limit can be adjusted accordingly.Table 4 shows the moisture contents of stoppers sub-jected to specific stopper autoclaving and drying processes. Vacuum drying mainly removes the surface moisture on stoppers. Drying 16 hours at 100oC achieves a free moisture amount of 0.03%. This amount allows
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M.J. Pikal and S. Shah, “Moisture transfer from stop-per to product and resulting stability implications,”Develop. Biol. Standard. 74, 165-179, (1991).2.
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“Injection Containers for Injectables and Accesso-ries. Part 5: Freeze Drying Closures for Injection Vials,” ISO 8362-5:1995(E).
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M.S. Hora and S.N. Wolfe, “Critical steps in the preparation of elastomeric closures for biopharmaceutical freeze-dried products,” Freeze-drying/lyophilization of pharmaceutical and bio-logical products,” L. Rey and J.C. May, Ed.,Marcel Dekker, New York, pp 409-422, (1999).6.
A.G. Thormas and K. Muniandy, “Absorption and Desorption of Water in Rubbers,” Polymer , 28,408-415, (1987).
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英语中的比较级与最高级 详解
比较级与最高级 1.as...as 与(not) as(so)...as as...as...句型中，as的词性 第一个as是副词，用在形容词和副词的原级前，常译为“同样地”。第二个as是连词，连接与前面句子结构相同的一个句子(相同部分常省略)，可译为“同..... He is as tall as his brother is (tall) . (后面的as 为连词) 只有在否定句中，第一个as才可换为so 改错: He is so tall as his brother.（X） 2.在比较状语从句中，主句和从句的句式结构一般是相同的 与as...as 句式中第二个as一样，than 也是连词。as和than这两个连词后面的从句的结构与前面的句子大部分情况下结构是相同的，相同部分可以省略。 He picked more apples than she did. 完整的表达为: He picked more apples than she picked apples. 后而的picked apples和前面相同，用did 替代。 He walked as slowly as she did.完整表达为: He walked as slowly as she walked slowly. she后面walked slowly与前面相同，用did替代。
3.谓语的替代 在as和than 引导的比较状语从句中，由于句式同前面 主句相同，为避免重复，常把主句中出现而从句中又出现的动词用do的适当形式来代替。 John speaks German as fluently as Mary does. 4.前后的比较对象应一致 不管后面连词是than 还是as,前后的比较对象应一致。The weather of Beijing is colder than Guangzhou. x than前面比较对象是“天气”，than 后面比较对象是“广州”，不能相比较。应改为: The weather of Bejing is colder than that of Guangzhou. 再如: His handwriting is as good as me. 应改为: His handwriting is as good as mine. 5.可以修饰比较级的词 常用来修饰比较级的词或短语有: Much,even,far,a little,a lot,a bit,by far,rather,any,still,a great deal等。 by far的用法: 用于强调，意为“...得多”“最最...”“显然”等，可修饰形容词或副词的比较级和最高级，通常置于其后，但是若比较级或最高级前有冠词，则可置于其前或其后。
The way常见用法
The way 的用法 Ⅰ常见用法： 1)the way+ that 2)the way + in which（最为正式的用法） 3)the way + 省略（最为自然的用法） 举例：I like the way in which he talks. I like the way that he talks. I like the way he talks. Ⅱ习惯用法： 在当代美国英语中，the way用作为副词的对格，“the way+ 从句”实际上相当于一个状语从句来修饰整个句子。 1)The way =as I am talking to you just the way I’d talk to my own child. He did not do it the way his friends did. Most fruits are naturally sweet and we can eat them just the way they are—all we have to do is to clean and peel them. 2）The way= according to the way/ judging from the way The way you answer the question, you are an excellent student. The way most people look at you, you’d think trash man is a monster. 3）The way =how/ how much No one can imagine the way he missed her. 4）The way =because
人教版(新目标)初中英语形容词与副词的比较级与最高级
人教版（新目标）初中英语形容词与副词的比较级与最高级 （一）规则变化： 1．绝大多数的单音节和少数双音节词，加词尾-er ，-est tall—taller—tallest 2．以不发音的e结尾的单音节词和少数以-le结尾的双音节词只加-r，-st nice—nicer—nicest , able—abler—ablest 3．以一个辅音字母结尾的重读闭音节词或少数双音节词，双写结尾的辅音字母，再加-er，-est big—bigger—biggest 4．以辅音字母加y结尾的双音节词，改y为i再加-er，-est easy—easier—easiest 5．少数以-er，-ow结尾的双音节词末尾加-er，-est clever—cleverer—cleverest, narrow—narrower—narrowest 6．其他双音节词和多音节词，在前面加more，most来构成比较级和最高级 easily—more easily—most easily （二）不规则变化 常见的有： good / well—better—best ; bad (ly)/ ill—worse—worst ; old—older/elder—oldest/eldest many / much—more—most ; little—less—least ; far—farther/further—farthest/furthest
用法： 1．原级比较：as + adj./adv. +as（否定为not so/as + adj./adv. +as）当as… as中间有名字时，采用as + adj. + a + n.或as + many / much + n. This is as good an example as the other is . I can carry as much paper as you can. 表示倍数的词或其他程度副词做修饰语时放在as的前面 This room is twice as big as that one. 倍数+as+adj.+as = 倍数+the +n.+of Your room is twice as larger as mine. = Your room is twice the size of mine. 2．比较级+ than 比较级前可加程度状语much, still, even, far, a lot, a little, three years. five times,20%等 He is three years older than I (am). 表示“（两个中）较……的那个”时，比较级前常加the（后面有名字时前面才能加冠词） He is the taller of the two brothers. / He is taller than his two brothers. Which is larger, Canada or Australia? / Which is the larger country, Canada or Australia? 可用比较级形式表示最高级概念，关键是要用或或否定词等把一事物（或人）与其他同类事物（或人）相分离 He is taller than any other boy / anybody else.
英语中的比较级和最高级
大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基础上变化的。分为规则变化和不规则变化。 规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加 -er 和 -est 构成。 great (原级) (比较级) (最高级) 2) 以 -e 结尾的单音节形容词的比较级和最高级是在词尾加 -r 和 -st 构成。wide (原级) (比较级) (最高级) 3)少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加 -er 和 -est 构成。 clever(原级) (比较级) (最高级) 4) 以 -y 结尾,但 -y 前是辅音字母的形容词的比较级和最高级是把 -y 去掉,加上 -ier 和-est 构成. happy (原形) (比较级) (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该辅音字母然后再加 -er和-est。 big (原级) (比较级) (最高级) 6) 双音节和多音节形容词的比较级和最高级需用more 和 most 加在形容词前面来构成。 beautiful (原级) (比较级) (比较级) difficult (原级) (最高级) (最高级) 常用的不规则变化的形容词的比较级和最高级: 原级------比较级------最高级 good------better------best many------more------most much------more------most bad------worse------worst far------farther, further------farthest, furthest 形容词前如加 less 和 least 则表示"较不"和"最不 形容词比较级的用法: 形容词的比较级用于两个人或事物的比较,其结构形式如下: 主语+谓语(系动词)+ 形容词比较级+than+ 对比成分。也就是, 含有形容词比较级的主句+than+从句。注意从句常常省去意义上和主句相同的部分, 而只剩下对比的成分。
The way的用法及其含义(二)
The way的用法及其含义（二） 二、the way在句中的语法作用 the way在句中可以作主语、宾语或表语： 1.作主语 The way you are doing it is completely crazy.你这个干法简直发疯。 The way she puts on that accent really irritates me. 她故意操那种口音的样子实在令我恼火。The way she behaved towards him was utterly ruthless. 她对待他真是无情至极。 Words are important, but the way a person stands, folds his or her arms or moves his or her hands can also give us information about his or her feelings. 言语固然重要,但人的站姿,抱臂的方式和手势也回告诉我们他(她)的情感。 2.作宾语 I hate the way she stared at me.我讨厌她盯我看的样子。 We like the way that her hair hangs down.我们喜欢她的头发笔直地垂下来。 You could tell she was foreign by the way she was dressed. 从她的穿著就可以看出她是外国人。 She could not hide her amusement at the way he was dancing. 她见他跳舞的姿势，忍俊不禁。 3.作表语 This is the way the accident happened.这就是事故如何发生的。 Believe it or not, that's the way it is. 信不信由你, 反正事情就是这样。 That's the way I look at it, too. 我也是这么想。 That was the way minority nationalities were treated in old China. 那就是少数民族在旧中
英语比较级和最高级的用法归纳
英语比较级和最高级的用法归纳 在学习英语过程中，会遇到很多的语法问题，比如比较级和最高级的用法，对于 这些语法你能够掌握吗？下面是小编整理的英语比较级和最高级的用法，欢迎阅读！ 英语比较级和最高级的用法 一、形容词、副词的比较级和最高级的构成规则 1.一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级 在后面加-est; (1)单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest (2)双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2.以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st; 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3.在重读闭音节(即：辅音+元音+辅音)中，先双写末尾的辅音字母，比较级加-er，最高级加-est; 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4.以“辅音字母+y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est; 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5.其他双音节词和多音节词，比较级在前面加more，最高级在前面加most; 如：bea utiful→more beautiful→most beautiful different→more different→most different easily→more easily→most easily 注意：(1)形容词最高级前通常必须用定冠词 the，副词最高级前可不用。 例句： The Sahara is the biggest desert in the world. (2) 形容词most前面没有the，不表示最高级的含义，只表示"非常"。 It is a most important problem. =It is a very important problem.
(完整版)the的用法
定冠词the的用法： 定冠词the与指示代词this ,that同源,有“那(这)个”的意思,但较弱,可以和一个名词连用,来表示某个或某些特定的人或东西. (1)特指双方都明白的人或物 Take the medicine.把药吃了. (2)上文提到过的人或事 He bought a house.他买了幢房子. I've been to the house.我去过那幢房子. (3)指世界上独一无二的事物 the sun ,the sky ,the moon, the earth (4)单数名词连用表示一类事物 the dollar 美元 the fox 狐狸 或与形容词或分词连用,表示一类人 the rich 富人 the living 生者 (5)用在序数词和形容词最高级,及形容词等前面 Where do you live?你住在哪? I live on the second floor.我住在二楼. That's the very thing I've been looking for.那正是我要找的东西. (6)与复数名词连用,指整个群体 They are the teachers of this school.(指全体教师) They are teachers of this school.(指部分教师) (7)表示所有,相当于物主代词,用在表示身体部位的名词前 She caught me by the arm.她抓住了我的手臂. (8)用在某些有普通名词构成的国家名称,机关团体,阶级等专有名词前 the People's Republic of China 中华人民共和国 the United States 美国 (9)用在表示乐器的名词前 She plays the piano.她会弹钢琴. (10)用在姓氏的复数名词之前,表示一家人 the Greens 格林一家人(或格林夫妇) (11)用在惯用语中 in the day, in the morning... the day before yesterday, the next morning... in the sky... in the dark... in the end... on the whole, by the way...
英语比较级和最高级的用法
More than的用法 A. “More than+名词”表示“不仅仅是” 1)Modern science is more than a large amount of information. 2)Jason is more than a lecturer; he is a writer, too. 3) We need more than material wealth to build our country.建设我们国家，不仅仅需要物质财富. B. “More than+数词”含“以上”或“不止”之意，如： 4)I have known David for more than 20 years. 5)Let's carry out the test with more than the sample copy. 6) More than one person has made this suggestion. 不止一人提过这个建议. C. “More than+形容词”等于“很”或“非常”的意思，如： 7)In doing scientific experiments, one must be more than careful with the instruments. 8)I assure you I am more than glad to help you. D. more than + (that)从句，其基本意义是“超过（=over）”，但可译成“简直不”“远非”.难以，完全不能（其后通常连用情态动词can） 9) That is more than I can understand . 那非我所能懂的. 10) That is more than I can tell. 那事我实在不明白。 11) The heat there was more than he could stand. 那儿的炎热程度是他所不能忍受的 此外，“more than”也在一些惯用语中出现，如： more...than 的用法 1. 比……多，比……更 He has more books than me. 他的书比我多。 He is more careful than the others. 他比其他人更仔细。 2. 与其……不如 He is more lucky than clever. 与其说他聪明，不如说他幸运。 He is more （a）scholar than （a）teacher. 与其说他是位教师，不如说他是位学者。 注：该句型主要用于同一个人或物在两个不同性质或特征等方面的比较，其中的比较级必须用加more 的形式，不能用加词尾-er 的形式。 No more than/not more than 1. no more than 的意思是“仅仅”“只有”“最多不超过”，强调少。如： --This test takes no more than thirty minutes. 这个测验只要30分钟。 --The pub was no more than half full. 该酒吧的上座率最多不超过五成。-For thirty years，he had done no more than he （had）needed to. 30年来，他只干了他需要干的工作。 2. not more than 为more than （多于）的否定式，其意为“不多于”“不超过”。如：Not more than 10 guests came to her birthday party. 来参加她的生日宴会的客人不超过十人。 比较： She has no more than three hats. 她只有3顶帽子。（太少了） She has not more than three hats. 她至多有3顶帽子。（也许不到3顶帽子） I have no more than five yuan in my pocket. 我口袋里的钱最多不过5元。（言其少） I have not more than five yuan in my pocket. 我口袋里的钱不多于5元。（也许不到5元） more than, less than 的用法 1. （指数量）不到，不足 It’s less than half an hour’s drive from here. 开车到那里不到半个钟头。 In less than an hour he finished the work. 没要上一个小时，他就完成了工作。 2. 比……（小）少 She eats less than she should. 她吃得比她应该吃的少。 Half the group felt they spent less than average. 半数人觉得他们的花费低于平均水平。 more…than,/no more than/not more than (1)Mr．Li is ________ a professor; he is also a famous scientist． (2)As I had ________ five dollars with me, I couldn’t afford the new jacket then． (3)He had to work at the age of ________ twelve． (4)There were ________ ten chairs in the room．However, the number of the children is twelve． (5)If you tel l your father what you’ve done, he’ll be ________ angry． (6)－What did you think of this novel? －I was disappointed to find it ________ interesting ________ that one． 倍数表达法 1. “倍数+形容词（或副词）的比较级+than+从句”表示“A比B大（长、高、宽等）多少倍” This rope is twice longer than that one.这根绳是那根绳的三倍（比那根绳长两倍）。The car runs twice faster than that truck.这辆小车的速度比那辆卡车快两倍（是那辆卡车的三倍）。 2. “倍数+as+形容词或副词的原级+as+从句”表示“A正好是B的多少倍”。
“the way+从句”结构的意义及用法
“tｈｅwａｙ+从句”结构的意义及用法 首先让我们来看下面这个句子: Ｒead the foｌloｗｉnｇpassagｅａnd talkａbout ｉt wi ｔh your classmaｔes．Try tｏｔeｌl whaｔyｏu thiｎk ｏf Tom aｎd ｏｆｔhe ｗay the chiｌｄrenｔrｅated ｈim. 在这个句子中，ｔhe waｙ是先行词,后面是省略了关系副词that或in whｉch的定语从句。 下面我们将叙述“the ｗaｙ+从句”结构的用法。 1.tｈe wａy之后，引导定语从句的关系词是tｈat而不是hoｗ,因此，<<现代英语惯用法词典＞＞中所给出的下面两个句子是错误的：Ｔhｉs is ｔｈeｗayｈowｉtｈａppened. This is the way how he ａlwａｙs treats me. 2．在正式语体中,thaｔ可被in which所代替;在非正式语体中，ｔhat则往往省略。由此我们得到theｗay后接定语从句时的三种模式：1) tｈe ｗaｙ＋ｔhａt-从句２）the way +ｉn whiｃh－从句3) the ｗay +从句 例如：Ｔｈe way(in whiｃh ，thａt) ｔhｅｓｅｃomｒade ｓloｏｋａｔｐrobｌems is wrong．这些同志看问题的方法
不对。 Ｔｈｅｗａy(that ,ｉn ｗhiｃh)yoｕ’ｒe doinｇit is comple ｔeｌy crａzy.你这么个干法,简直发疯。 Wｅａdmiｒｅd him for thｅｗay ｉｎｗhｉch he fａｃeｓdiｆficultieｓ． Waｌlａｃe ａｎd Ｄarwiｎｇreed ｏn the way ｉｎwhi ｃh ｄｉfｆｅrｅnt forms ｏf life had ｂegｕn.华莱士和达尔文对不同类型的生物是如何起源的持相同的观点。 Thｉs is ｔｈe ｗaｙ（tｈａｔ) hｅdｉd it. I lｉkeｄｔhe waｙ(ｔhat) ｓｈeｏｒganized ｔhe ｍeetｉng． 3.theｗay(tｈat)有时可以与hｏw(作“如何”解）通用。例如： That’s tｈe ｗaｙ(tｈaｔ) shｅspoke. = Tｈat’s how shｅspoke.
初中英语比较级和最高级讲解与练习
初中英语比较级和最高级讲解与练习 形容词比较级和最高级 一．绝大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 1. 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 2. 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基 础上变化的。分为规则变化和不规则变化。 二．形容词比较级和最高级规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加-er 和-est 构成。 great (原级) greater(比较级) greatest(最高级) 2) 以-e 结尾的单音节形容词的比较级和最高级是在词尾加-r 和-st 构成。 wide (原级) wider (比较级) widest (最高级) 3) 少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加 -er 和-est构成。 clever(原级) cleverer(比较级) cleverest(最高级)， slow(原级) slower(比较级) slowest (最高级) 4) 以-y 结尾,但-y 前是辅音字母的形容词的比较级和最高级是把-y 去掉,加上-ier 和-est 构成. happy (原形) happier (比较级) happiest (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该 辅音字母然后再加-er和-est。 原形比较级最高级原形比较级最高级 big bigger biggest hot hotter hottest red redder reddest thin thinner thinnest 6) 双音节和多音节形容词的比较级和最高级需用more 和most 加在形容词前面来构 成。 原形比较级最高级 careful careful more careful most careful difficult more difficult most difficult delicious more delicious most delicious 7)常用的不规则变化的形容词的比较级和最高级: 原级比较级最高级 good better best 好的 well better best 身体好的 bad worse worst 坏的 ill worse worst 病的 many more most 许多 much more most 许多 few less least 少数几个 little less least 少数一点儿 （little littler littlest 小的） far further furthest 远（指更进一步，深度。亦可指更远） far farther farthest 远（指更远，路程）
way 用法
表示“方式”、“方法”，注意以下用法： 1.表示用某种方法或按某种方式，通常用介词in(此介词有时可省略)。如： Do it (in) your own way. 按你自己的方法做吧。 Please do not talk (in) that way. 请不要那样说。 2.表示做某事的方式或方法，其后可接不定式或of doing sth。 如： It’s the best way of studying [to study] English. 这是学习英语的最好方法。 There are different ways to do [of doing] it. 做这事有不同的办法。 3.其后通常可直接跟一个定语从句(不用任何引导词)，也可跟由that 或in which 引导的定语从句，但是其后的从句不能由how 来引导。如： 我不喜欢他说话的态度。 正：I don’t like the way he spoke. 正：I don’t like the way that he spoke. 正：I don’t like the way in which he spoke. 误：I don’t like the way how he spoke. 4.注意以下各句the way 的用法： That’s the way (=how) he spoke. 那就是他说话的方式。 Nobody else loves you the way(=as) I do. 没有人像我这样爱你。 The way (=According as) you are studying now, you won’tmake much progress. 根据你现在学习情况来看，你不会有多大的进步。 2007年陕西省高考英语中有这样一道单项填空题： ——I think he is taking an active part insocial work. ——I agree with you_____. A、in a way B、on the way C、by the way D、in the way 此题答案选A。要想弄清为什么选A，而不选其他几项，则要弄清选项中含way的四个短语的不同意义和用法，下面我们就对此作一归纳和小结。 一、in a way的用法 表示：在一定程度上，从某方面说。如： In a way he was right.在某种程度上他是对的。注：in a way也可说成in one way。 二、on the way的用法 1、表示：即将来(去)，就要来(去)。如： Spring is on the way.春天快到了。 I'd better be on my way soon.我最好还是快点儿走。 Radio forecasts said a sixth-grade wind was on the way.无线电预报说将有六级大风。 2、表示：在路上，在行进中。如： He stopped for breakfast on the way.他中途停下吃早点。 We had some good laughs on the way.我们在路上好好笑了一阵子。 3、表示：(婴儿)尚未出生。如： She has two children with another one on the way.她有两个孩子，现在还怀着一个。 She's got five children，and another one is on the way.她已经有5个孩子了，另一个又快生了。 三、by the way的用法
英语比较级和最高级
形容词比较级和最高级的形式 一、形容词比较级和最高级的构成 形容词的比较级和最高级变化形式规则如下 构成法原级比较级最高级 ①一般单音节词末尾加 er 和 est strong stronger strongest ②单音节词如果以 e结尾，只加 r 和 st strange stranger strangest ③闭音节单音节词如末尾只有一个辅音字母， 须先双写这个辅音字母，再加 er和 est sad big hot sadder bigger hotter saddest biggest hottest ④少数以 y, er(或 ure), ow, ble结尾的双音节词， 末尾加 er和 est(以 y结尾的词，如 y前是辅音字母， 把y变成i，再加 er和 est，以 e结尾的词仍 只加 r和 st) angry Clever Narrow Noble angrier Cleverer narrower nobler angriest cleverest narrowest noblest ⑤其他双音节和多音节词都在前面加单词more和most different more different most different 1) The most high 〔A〕mountain in 〔B〕the world is Mount Everest，which is situated 〔C〕in Nepal and is twenty nine thousand one hundred and fourty one feet high 〔D〕 . 2) This house is spaciouser 〔A〕than that 〔B〕white 〔C〕one I bought in Rapid City，South Dakota 〔D〕last year. 3) Research in the social 〔A〕sciences often proves difficulter 〔B〕than similar 〔C〕work in the physical 〔D〕sciences. 二、形容词比较级或最高级的特殊形式：
高中英语的比较级和最高级用法总结
比较级和最高级 1.在形容词词尾加上―er‖ ―est‖ 构成比较级、最高级： bright（明亮的）—brighter—brightest broad（广阔的）—broader—broadest cheap（便宜的）—cheaper—cheapest clean（干净的）—cleaner—cleanest clever（聪明的）—cleverer—cleverest cold（寒冷的）—colder—coldest cool（凉的）—cooler—coolest dark（黑暗的）—darker—darkest dear（贵的）—dearer—dearest deep（深的）—deeper—deepest fast（迅速的）—faster—fastest few（少的）—fewer—fewest great（伟大的）—greater—greatest hard（困难的,硬的）—harder—hardest high（高的）—higher—highest kind（善良的）—kinder—kindest light（轻的）—lighter—lightest long（长的）—longer—longest loud（响亮的）—louder—loudest low（低的）—lower—lowest near（近的）—nearer—nearest new（新的）—newer—newest poor（穷的）—poorer—poorest quick（快的）—quicker—quickest quiet（安静的）—quieter—quietest rich（富裕的）—richer—richest short（短的）—shorter—shortest slow（慢的）—slower—slowest small（小的）—smaller—smallest smart（聪明的）—smarter—smartest soft（柔软的）—softer—softest strong（强壮的）—stronger—strongest sweet（甜的）—sweeter—sweetest tall（高的）-taller-tallest thick（厚的）—thicker—thickest warm（温暖的）—warmer—warmest weak（弱的）—weaker—weakest young（年轻的）—younger—youngest 2.双写最后一个字母,再加上―er‖ ―est‖构成比较级、最高级： big（大的）—bigger—biggest fat（胖的）—fatter—fattest hot（热的）—hotter—hottest red（红的）—redder—reddest sad（伤心的）—sadder—saddest thin（瘦的）—thinner—thinnest wet（湿的）—wetter—wettest mad（疯的）—madder—maddest 3.以不发音的字母e结尾的形容词,加上―r‖ ―st‖ 构成比较级、最高级：able（能干的）—abler—ablest brave（勇敢的）—braver—bravest close（接近的）—closer—closest fine（好的,完美的）—finer—finest large（巨大的）—larger—largest late（迟的）—later—latest nice（好的）—nicer—nicest ripe（成熟的）—riper—ripest
The way的用法及其含义(一)
The way的用法及其含义（一） 有这样一个句子：In 1770 the room was completed the way she wanted. 1770年，这间琥珀屋按照她的要求完成了。 the way在句中的语法作用是什么？其意义如何？在阅读时，学生经常会碰到一些含有the way 的句子，如：No one knows the way he invented the machine. He did not do the experiment the way his teacher told him.等等。他们对the way 的用法和含义比较模糊。在这几个句子中，the way之后的部分都是定语从句。第一句的意思是，“没人知道他是怎样发明这台机器的。”the way的意思相当于how；第二句的意思是，“他没有按照老师说的那样做实验。”the way 的意思相当于as。在In 1770 the room was completed the way she wanted.这句话中，the way也是as的含义。随着现代英语的发展，the way的用法已越来越普遍了。下面，我们从the way的语法作用和意义等方面做一考查和分析： 一、the way作先行词，后接定语从句 以下3种表达都是正确的。例如：“我喜欢她笑的样子。” 1. the way+ in which +从句 I like the way in which she smiles. 2. the way+ that +从句 I like the way that she smiles. 3. the way + 从句(省略了in which或that) I like the way she smiles. 又如：“火灾如何发生的，有好几种说法。” 1. There were several theories about the way in which the fire started. 2. There were several theories about the way that the fire started.
(完整版)初中英语比较级和最高级的用法
英语语法---比较级和最高级的用法 在英语中通常用下列方式表示的词:在形容词或副词前加more(如 more natural,more clearly )或加后缀 -er(newer,sooner )。典型的是指形容词或副词所表示的质、量或关系的增加。英语句子中，将比较两个主体的方法叫做“比较句型”。其中，像“A比B更……”的表达方式称为比较级；而“A最……”的表达方式则称为最高级。组成句子的方式是将形容词或副词变化成比较级或最高级的形态。 一、形容词、副词的比较级和最高级的构成规则 1．一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级在后面加-est； （1）单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest （2）双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2．以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st； 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3．在重读闭音节（即：辅音＋元音＋辅音）中，先双写末尾的辅音字母，比较级加-er，最高级加-est； 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4．以“辅音字母＋y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est； 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5．其他双音节词和多音节词，比较级在前面加more，最高级在前面加most； 如：beautiful→more beautiful→most beautiful different→more different→most different easily→more easily→most easily