一直以来，英语中复合句的写作对很多学生来说一直是一个不小的难题。尤其是引导词"since"的用法更是让大家头疼不已，因为它既可以引导时间状语又可以引导原因状语从句，到底如何区分呢？下面就为大家详细整理一下"since"的各种用法。

　　1. since译作"自从…以来"

　　(1) 接时间点，谓语v. 用现在完成时，而且须是延续性动词；

　　如 I have stayed in that country since 1995.

　　(2) 接一段时间+ ago，谓语v. 用现在完成时，而且须是延续性动词；

　　如 They have lived in that house since two years ago.

　　(3) 接时间状语从句，主句的谓语v. 用现在完成时，而且须是延续性动词；从句的谓语v.用一般过去时，而且须是终止性动词；

　　如 I have loved her since I met her last time./ Lily has stayed at home since she left school.

　　(4) 用于句型"It's / It has been + 一段时间 + since + 时间状语从句"中，译作"自从......以来，已经......(时间)了"。主句的谓语v. 用一般现在时或现在完成时，从句的谓语v. 用一般过去时，而且须是终止性动词；

　　如 It's / has been three months since he moved to this city.

　　(5) 用于句型"一段时间 + has passed since + 时间状语从句"中，译作"自从......以来，......（时间）已经过去了"。主句的谓语v. 用现在完成时，而且动词必须是has passed；从句的谓语v.用一般过去时，而且须是终止性动词；

　　如，上个例句还可写成：Three months has passed since he moved to this city.

　　(6) 当since用于否定句时，主句的谓语v. 可以是终止性动词；

　　如 He hasn't seen the film since last month.

　　(7) 相关词组：

　　"从那时起"：ever since/ since then/from then on

　　注：ever since作为一个词组，放句尾可单独使用。如I have given up smoking ever since.另外还可在since后接句子，since前加eve，只是加重语气而已。如 I have given up smoking ever since I caught a bad cough.

　　2. since译作"由于，因为"

　　(8) since还可引导原因状语从句，相当于because。

　　如 Since he was lazy,he didn't finish his homework.