before：

prep.在…以前;在…面前(或前面);

conj.在…以前;到…为止;

adv.以前;过去;

相关介绍

It would be a good idea to call before we leave.

我们出发之前打个电话是个好主意。

Profits were at the same level as the year before.

利润和前一年的持平。

Have you ever used this software before?

你以前用过这种软件吗？