表示“來不及； 尚未…..就…”

　　Before I could get in a word , he had measured me .

　　He ran off before I could stop him .

　　She left the company before I could have a word with her .

　　表示“剛…就…”

　　I had hardly sat down before the bell rang.

　　5. 表示“不知不覺就…..； 還沒弄清就……”

　　Time passed quickly and three months went by before Aqiao knew it.

　　表示“寧愿…，決不…，與其…，毋寧….”常與will 或would 連用。

　　I would die before I would tell

　　I’d shoot myself before I apologized to him.

　　I would / will die before I surrender .

　　表示“否則；以免”

　　Do it now before you forget . I will write it down before I forget it .

　　用于句型“it was +時(shí)間段+ before …” 表示 “過了多久才…”

　　It was three days before he came back. .

　　用于句型 “ it was not long +時(shí)間段+ before …” 意為“不久就….”

　　It was not long before he sensed the danger of the position .

　　10. 用于句型“it will be(not )+時(shí)間段+ before….”表示“要過多久/ 不久…才…”

　　It will be half a year before you graduate from this school .

　　It will be not long before you find you are wrong .