χρηστ-ικός · chrēst-ikos — LSJ
knowing how to use, understanding the use of
knowing how to use, understanding the use of a thing, τῶν ὑπαρχόντων Arist. Oec. 1344b26; δεσποτικὴ ἐπιστήμη ἡ χ. δούλων Id. Pol. 1255b31: abs., δύναμις χ., opp. ὑπηρετική, Procl. in Prm. p.735 S.: also c. dat. (like the Verb), M.Ant. 7.55.
2 useful, serviceable
of things, useful, serviceable, σώματος ἕξις Plu. Cat.Ma. 1: Sup., μέλι -ώτατον Id. Aud.poet. 2.32e. Adv. -κῶς ib. Profect. 80b: Comp. -ώτερον Arr. Epict. 2.9.19.