βαθύ

From LSJ

ὥσπερ σελήνη γ' ἡλίῳ· τὴν μὲν χρόαν ἰδεῖν ὁμοιόν ἔστι θάλπει δ' οὐδαμῶς → like the moon to the sun: its color is similar to the eye, but it does not give off any heat

Source

Russian (Dvoretsky)

βᾰθύ: τό глубина; τὸ β. τῆς ἡλικίας Arph. пожилой возраст.