分类：教育/科学-学习帮助
问题：给我讲一下before的用法吧，越多越好，最好能与since比较? 
给我讲一下before的用法吧，越多越好，最好能与since比较。
回答：后接“时间点”，可用于任何时态，如： 　　She got  to  his    before 5'o clock. 　　她５点钟以前就到了办公室。 单独使用，常与现在完成时连用，也可与一般过去时连用，如：     I have never met him before.　 我以前从未见过他。也可放在表“时间段”的词语后，与过去完成时连用，表示从过去某时刻算起的若干时间以前，如：     He said he had finished his job 2 days before.　　他说他两天前就完成了他的工作。 Before 在英语中是一个比较常用的虚词，它既可作介词或副词用，也可作从属连词用。1. 表示“在…..之前就…..”。Mary had finished her homework before her mother returned.2. 表示“过了多久后才…….. ，动作进行到什么程度才……”The man almost knocked me down before he saw me .They walked about 30 miles to the west before they saw a village .They worked day and night about three days before everything returned to normal .3. 表示“来不及； 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 .4. 表示“刚…就…”I had hardly sat down before the bell rang.5. 表示“不知不觉就…..； 还没弄清就……”Time passed quickly and three months went by before Aqiao knew it.6. 表示“宁愿…，决不…，与其…，毋宁….”常与will 或would 连用。I would die before I would tell I’d shoot myself before I apologized to him.I would / will die before I surrender .7. 表示“否则；以免”Do it now before you forget . I will write it down before I forget it .8. 用于句型“it was +时间段+ before …” 表示 “过了多久才…”It was three days before he came back. .9. 用于句型 “ it was not long +时间段+ before …” 意为“不久就….”It was not long before he sensed the danger of the position .10. 用于句型“it will be(not )+时间段+ before….”表示“要过多久/ 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 .