αἰνιγμός
From LSJ
Ζῆν οὐκ ἄξιος, ὅτῳ μηδὲ εἷς ἐστι χρηστὸς φίλος → Life is not worth living if you do not have at least one friend.
English (LSJ)
ὁ,
A riddle, mostly like αἴνιγμα in pl., δι' αἰνιγμῶν ἐρεῖν Ar. Ra.61, cf. Pl.Ti.72b, Aeschin.3.121; ἐν αἰνιγμοῖσι σημαίνειν τι E. Rh.754; ἐν αἰ. λαλεῖν Anaxil.22.23: sg., Callisth. ap. Ath.10.452a.