after

介词

1.在...以后

After graduation he went abroad. 毕业后他去了国外。

At half after ten it began to rain. 在十点半下起雨来。

2.在...后面;随...之后

After you with the paper, please. 请您看完报纸后给我。

She entered the hall after her mother. 她跟随在她母亲之后进入厅内。

3.低于;次于

A captain comes after a major. 上尉军衔低于少校。

4.鉴于,由于

After what had happened he could not continue to work there. 鉴于所发生的事情,他不可能继续在那里工作下去了。

5.仿照,模仿

This is a painting after Picasso. 这是一幅仿毕加索的画。

6.依照;按照...的名字

The kid was named after his grandfather. 这孩子是以他祖父的名字命名的。

7.尽管

After all our efforts, the experiment failed. 尽管我们做了努力,试验还是失败了。

8.搜寻,寻找

Mary is after a better job. 玛丽在寻找一个更好的工作。

连词

1.在...之后

I will tell you after they leave. 他们走后我再告诉你。

副词

1.以后,之后

They arrived shortly after. 不久以后他们抵达了。

2.在后面,随后

Tom went on Monday, and Mary left the day after. 汤姆星期一走的,玛丽第二天就离开了。

形容词

1.以后的

His health was declining in after years. 在以后的岁月,他的健康不断衰退。

2.后部的

A few passengers would have a stroll on the after deck before the evening meal. 几位乘客将在晚饭前到后甲板上散步。

before

介词

1.在...以前

Only two days remained before the examination. 考前只剩下两天了。

2.(指顺序、重要性等)在...之前,先于

Your name comes before mine. 你的名字在我之前。

Pride comes before a fall. 骄必败。

3.由...考虑中

We will put the matter before the committee. 我将把此事提交委员会考虑。

4.在...前面;在...面前

She said she had never spoken before an audience. 她说她从未在大庭广众讲演过。

副词

1.较早

Come at two o'clock, not before. 两点钟来,不必再早了。

2.以前;曾经

He was never late before. 过去他从不迟到。

Have you two met before? 你们两人以前见过面吗?

3.在前;向前

Several soldiers went before to scout. 数名士兵在前面探路。

连词

1.在...以前

Check it carefully before you hand it in. 交来之前仔细核对一下。

2.与其...宁可

I'd die before I'd tell. 我宁死也决不会说出来。

3.否则,要不然

Get out before I call the police. 滚开,否则我叫警察。参考资料：http://zhidao.baidu.com/question/243607605.html