after和since的区别.
问题描述：
after和since的区别.
答
since的时态必定是现在完成时和过去完成时:he has taught english since 2000.
after后面加一段时间,时态是过去(完成)时,将来时:he will go to the underground station after ten o'clock.he went (has gone)to Paris after 2000.
since指的是已经完成了此事
after指的是已经完成了此事或没有完成而将要完成.