用法：
1、against作“反對(duì)”解時(shí)反義詞是for。
2、against用在fight，strive，struggle等詞后面，同with意思相同，不過(guò)against更強(qiáng)調(diào)一種困難中的`反抗。
We fight for the weak against the strong.
3、作為介詞，against后接的賓語(yǔ)有時(shí)可省略。
We have saved some money against our old age.
我們存了一些錢，以備老年之用。
Our defences must be reinforced against attack.
我們必須加強(qiáng)防御設(shè)施以抵御進(jìn)攻。
His eloquence did not avail against the facts.
他的雄辯在事實(shí)面前不起什么作用。