adv. & conj. formal
--adv. from what place? (whence did they come?).
--conj.
1. to the place from which (return whence you came).
2 (often prec. by place etc.) from which (the source whence these errors arise).
3 and thence (whence it follows that).
Usage:
Use of from whence as in the place from whence they came, though common, is generally considered incorrect.
Etymology: ME whannes, whennes f. whanne, whenne f. OE hwanon(e) whence, formed as WHEN + -S(3): cf. THENCE