φεῖ
From LSJ
Ὅσον ζῇς, φαίνου, μηδὲν ὅλως σὺ λυποῦ· πρὸς ὀλίγον ἐστὶ τὸ ζῆν, τὸ τέλος ὁ χρόνος ἀπαιτεῖ. → While you live, shine; have no grief at all; life exists only for a short while, and time demands its toll.
English (LSJ)
τό, name of the letter φ, Callias ap.Ath.10.453d, Hellad. ap. Phot.Bibl.530B.; φεῖ shd. be restored for φῖ in Pl.Cra.427a, etc.; a pun on φφ
A = Φιδίς (leg. Φειδίς) in AP7.429 (Alc.).