since
conj.
1.因为,所以,既是
2....以来,以后,自从...的时候起
prep.
1....以来,以后,...之后,自从
adv.
1.以后,此后,以来
2.(距今几年)以前;(从那时候起几年)以前
1.从…至今：
There have been many changes since the war.
从战争到现在发生了许多变化.
2.自从…,自…算来,自…以来：
It has been raining since morning.
从早晨到现在一直在下雨.
1.以后,在…以后的时间里：
She has rung me once since she left.
她离家后给我来过一次电话.
2.[常前接 ever] 自…以来,自…至今：
I've been busy ever since I came back.
自我回来后一直在忙.
3.因为；既然：
Since this is so,it's better to accept it.
既来之,则安之.