Ζῆν οὐκ ἄξιος, ὅτῳ μηδὲ εἷς ἐστι χρηστὸς φίλος → Life is not worth living if you do not have at least one friend.
P. μῖλαξ, σμῖλαξ, ἡ (Plato) τάξος.
The word is also found in Euripides, Bacchae 703, and Aristophanes, Nubes 1007, but apparently with a different meaning.