εὐθυντέον
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
English (LSJ)
A one must correct, τοὺς Εὐκλείδου ὅρους Iamb.in Nic.p.26P.
Greek (Liddell-Scott)
εὐθυντέον: ῥημ. ἐπιθ. τοῦ εὐθύνω, δεῖ εὐθύνειν, Ἰάμβλ. ἐν Νικομ. 34D.