v. & n.
v. 1 tr. help, benefit. 2 refl. (foll. by of) profit by; take advantage of. 3 intr. a provide help. b be of use, value, or profit.
n. (usu. in neg. or interrog. phrases) use, profit (of no avail; without avail; of what avail?).
[ ME f. obs. vail (v.) f. OF valoir be worth f. L valere ]