συνετή

From LSJ

ὑγίεια καὶ νοῦς ἀγαθὰ τῷ βίῳ δύο → health and brains are the two good things for life

Source

Russian (Dvoretsky)

συνετή: ἡ (sc. ἡλικία) разумный, т. е. зрелый возраст Anth.