from then till now (often prec. by ever):He was elected in 1978 and has been president ever since.
between a particular past time and the present; subsequently:She at first refused, but has since consented.
ago; before now:long since.
continuously from or counting from:It has been warm since noon.
between a past time or event and the present:There have been many changes since the war.
in the period following the time when:He has written once since he left.
continuously from or counting from the time when:He has been busy since he came.
because; inasmuch as:Since you're already here, you might as well stay.
1400–50; late Middle English syns, sinnes (adverb, adverbial) thereupon, afterwards, Middle English sithenes (adverb, adverbial and conj.) afterwards, from (the specified time), because, equivalent. to sithen after that, since (Old English siththan, origin, originally sīth thām after that; see sith) + -es -s1
8.See corresponding entry in Unabridged See because.