用作介词，意思是“从……以来，自从”，常与完成时连用.
如：I haven’t written home since Christmas.自圣诞节以来，我未曾写信回家.
用作副词，意思是“从那时以后(一直到现在)”，“其后(到现在之间)” ever since从那以后一直 (更加强调since的用法).
Things have not changed very much since.从那时起，情况并没有太大的改变.
His first book was a great success and he has been famous as a writer ever since.
他的第一本书非常畅销，从那时起他就成了一位名作家.
He got a job with the firm in 1970 and has worked there ever since.
他从1970年开始在那家公司任职，之后就一直在那里工作.
用作连词
引导原因状语从句，相当于now that，意思是“因为……，既然……，鉴于……”.
如：Since the rain has stopped，let’s go for a walk.既然雨停了，我们出去散散步吧.
Since we are young，we shouldn’t be too afraid of making mistakes.
因为我们还年轻，所以不应该太害怕犯错误.
