since
/sɪns/preposition, conjunction, & adverb
1
- in the intervening period between (the time mentioned) and the time under consideration, typically the present自从; 从那以后, 此后：
as prep. she has suffered from cystic fibrosis since 1984她自1984年起, 就得了囊肿性纤维化病
the worst property slump since the war
自战争以来最严重的房地产衰退
as conjunction I've felt better since I've been here自从我来到这儿后, 感觉好多了
as adv. she ran away on Friday and we haven't seen her since.她星期五逃走了, 自那以后我们再也没有看见她。
2
- conjunction for the reason that; because既然; 因为：
delegates were delighted, since better protection of rhino reserves will help protect other rare species.
代表们很高兴, 因为对犀牛保护区的更好保护将有助于保护其他珍稀物种。
3
- adverb ago之前, 以前：
the settlement had vanished long since.
这个小居民点很久以前就消失了。
词源
late Middle English: contraction of obsolete sithence, or from dialect sin （both from dialect sithen 'thereupon， afterwards， ever since'）.