before的用法：before可作介词，含义为“之前”、“在…面前”、“在前面”；before还可作连词，含义为“到…为止”、“到…之前”、“不然”、“不愿”；before也可作副词，含义为“过去”、“已经”。

before可作介词、连词和副词，译为之前;在…以前;在…面前(或前面);在…以前;到…为止;到…之前;以免;以前;过去;已经。例句有：

1、She's lived there since before the war.

她从战前起就一直住在那里。

2、Before you is a list of the points we have to discuss.

放在你面前的是一份我们要讨论的要点清单。

3、Your name is before mine on the list.

名单上你的名字在我之前。

4、The task before us is a daunting one.

我们面临的任务令人胆怯。

5、They had the advantage of playing before their home crowd.

他们有在主场观众面前比赛的优势。

6、They retreated before the enemy.

面对敌人，他们撤退了。

7、Did she leave a message before she went?

她走之前留言了吗？

8、It was some time before I realized the truth.

过了很长一段时间我才悟出真相。

9、It had been fine the week before.

前一个星期天气很好。

10、I think we've met before.

我觉得我们以前见过面。