1.词义必须准确、清楚（见“单词应用举例”中“affect，effect，impact”等词条）。

2.尽量选用单词的首要含义，避免利用单词不常见、不正式或文学含义（见“单词应用举例”中“although”，“because”等词条）。

3.避免使用双重否定（见“单词应用举例”中“not”词条）。

4.注意起修饰、限制作用的单词的位置（见“单词应用举例”中“only”词条）。

单词应用举例：

（1）affect，effect，impact

affect：动词，相当于influence，modify，change；effect：作动词时相当于bring about，作名词时相当于consequence，outcome，result；impact：名词，相当于a significant effect。例如：

The increased use of pesticides affects agricultural productivity.

The use of polychlorinated benzenes has an effect on the cancer rate.

The effect of the added acid was negligible.

The new procedure effected a 50%increase in yield.

The impact of pesticide use on health is felt throughout the world.

The acid did not have a great impact on the reaction rate.

（2）although

表转折时，避免用具较强时间含义的“while”代替“although”。如：

While the reactions of the anion were solvent-dependent，the corresponding reactions of the substituted derivatives were not.

建议改为：

Although the reactions of the anion were solvent-dependent，the corresponding reactions of the substituted derivatives were not.

或：The reactions of the anion were solvent-dependent，but（or whereas）the corresponding reactions of the substituted derivatives were not.

表示时间概念时用while，否则用and或although。

He continued the traverse while I collected samples.

At the conference the terrain scientist gave a talk on sampling procedures and（not while）the geophysicist spoke on new instrumentation.

Although（not while）we found no evidence of fossils in the filed，laboratory analysis revealed an abundant fauna.

（3）among，between

用“between”表示两个对象之间；“among”表示三个或多个对象之间。如：

Communication between scientists and the public is essential.

Communication among scientists，educators，and the public is essential.

Communication among scientists is essential.

用于只分为两类之间的多个项目时，用between。如：

We found coal between the beds of shale.

Saskatchewan lies between Alberta，Manitoba，the Northwest Territories，and the United States.

（4）and，or

用“and”或“or”时含义要明确，避免用斜线符号（/）代替，如：

Hot/cold extremes will damage the samples.

应改为：

Hot and cold extremes will damage the samples.

再如：

Our goal was to confirm the presence of the alkaloid in the leaves and/or roots.

应改为：

Our goal was to confirm the presence of the alkaloid in the leaves and roots.

或：Our goal was to confirm the presence of the alkaloid in either the leaves or the roots.

或：Our goal was to confirm the presence of the alkaloid in the leaves，the roots，or both.

（5）assure，ensure，insure(www.daowen.com)

assure：affirm（确认，向……保证）；ensure：make certain（确认）；insure：indemnify for money（给……保险；为……投保）。如：

He assured me that the work had been completed.

The procedure ensures that clear guidelines have been established

You cannot get a mortgage unless you insure your home.

（6）because，since

表示原因时，避免用具较强时间含义的“since”代替“because”。如：

Since solvent reorganization is a potential contributor，the selection of data is very important.

建议改为：

Because solvent reorganization is a potential contributor，the selection of data is very important.

（7）comprise，compose

comprise相当于“contain”，“consist of”或“composed of”，表示“由……组成”或“由……构成”，避免使用“be comprised of”。如：

（8）fewer，less

使用“fewer”表示数字，用“less”表示数量。如：

fewer than 50 animals；fewer than 100 samples

less product；less time；less work

但：当数字（量）和单位作为一体使用时，使用“less”。如：

less than 5 mg；less than 3 days

（9）greater than，more than

使用“greater than”或“more than”等精确性词汇表示数量，避免使用“over”或“in excess of”。如：

（10）not

①避免使用wasn't，aren't，can't等缩写形式，应采用全拼形式，如：was not，are not，can not等。

②避免使用双重否定。如：

（11）only

单词“only”位置不同，所表达的含义有较大差别。如：

Only the largest group was injected with the test compound.（表示no other group）

The largest group was only injected with the test compound.（表示not given the compound in any other way）

The largest group was injected with only the test compound.（表示no other compounds）

The largest group was injected with the only test compound.（表示no other test compounds）

（12）respectively

同一个句子中有两个或多个相关联的表述时，需用“respectively”分隔。如：

The excitation and emission were measured at 360 and 440 nm，respectively.（即：The excitation was measured at 360 nm and the emission was measured at 440 nm.）

但：表示“separately”或“independently”含义时，不能用“respectively”代替。如：

错误：The electrochemical oxidations of chromium and tungsten tricarbonyl complexes，respectively，were studied.

正确：The electrochemical oxidations of chromium and tungsten tricarbonyl complexes were studied separately.

（13）whether

whether用于引导两种或多种可能性；whether or not则表示“无论如何”（regardless of whether）。如：

I am not sure whether I should repeat the experiment.或：I am not sure whether to repeat the experiment.

I am not sure whether I should repeat the experiment or use a different statistical treatment.

I am going to repeat the experiment whether the results are positive or negative.

Whether or not the results are positive，I will repeat the experiment.

Whether or not I repeat the experiment，I will probably leave the laboratory late tonight.