μήκυνσις
From LSJ
μὴ τὴν ὄψιν καλλωπίζου, ἀλλ' ἐν τοῖς ἐπιτηδεύμασιν ἴσθι καλός → Don't beautify your face, but be beautiful in your habits (Thales, in Diog. Laertius 1.37)
English (LSJ)
-εως, ἡ, lengthening, in prosody, Sch.D.T.p.49 H.
Greek (Liddell-Scott)
μήκυνσις: -εως, ἡ, τὸ μηκύνειν, ἐν προσῳδίᾳ, Α. Β. 822.