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since then的用法例句 since then一般用什么时态sincethen表示从那个时间点到现在的情况，一般用现在完成时，表示过去的某件事对现在还有影响。如：Ihavenotgonetheresincethen.从那以后，我从来没有去过那里。
原因状语从句because, since, as和for的比较比较：because, since, as和for 1） because语势最强，用来说明人所不知的原因，回答why提出的问题。当原因是显而易见的或已为人们所知，就用as或 since。 I didn't go, because I wdelay；v./ n.拖延，延误，延迟，延期；耽搁;参考例句：The strike caused a great delay in the delivery of the mail.这次罢工严重地延误了邮件的投递。 I couldn't judge whether the delay was good or bad.我不能断定这样延迟是好还是坏。
比较since和forSince 用来说明动作起始时间，for用来说明动作延续时间长度。 I have lived here for more than twenty years. I have lived here since I was born..known；adj.大家知道的；知名的，已知的;参考例句：He is a known artist.他是一个知名的艺术家。 He is known both as a painter and as a statesman.他是知名的画家及政治家。
since的四种用法1) since +过去一个时间点 (如具体的年、月、日期、钟点、1980, last month, half past six)。 I have been here since 1989. 2) since +一段时间+ agpostgraduate；adj.大学毕业后的，大学研究院的；n.研究生;参考例句：I didn't put down that I had postgraduate degree.我没有写上我有硕士学位。 After college,Mary hopes to do postgraduate work in law school.大学毕业后， 玛丽想在法学院从事研究工作。
since的用法Sincethen前后一般接现在完成时,表示从那以后。例句:Fordhaschangedsincethen.自从那以后,福特有了变化。