ἐνεργής
From LSJ
ἡ κέρκος τῇ ἀλώπεκι μαρτυρεῖ → you can tell a fox by its tail, small traits give the clue to the character of a person
English (LSJ)
ές, later form of ἐνεργός,
A active, effective, μηχανὰς ἐνεργεῖς ποιοῦντες D.S. 17.44, etc.; of medicines, strong, POxy.1088.56 (i A.D.), Dsc.5.88, etc.: Comp. -έστερος more effective, πρός τινα Arist.Top.105a19: Sup. -έστατος, πρός τι D.S.1.88, cf. Dsc.1.19, A.D.Synt.291.9.