εἰ: if, if only, whether; conjunction used in the expression of a wish or a condition, and in indirect questions.— I. As particle of wishing, εἰ or εἰ γάρ, would that, O that, is foll. by the optative.—II. Interrogatively, whether, foll. by such construction as the meaning requires, e. g., κατάλεξονεἰ καὶ Λᾶέρτῃ αὐτὴν ὁδὸν ἄγγελος ἔλθω, am to go, Od. 16.138.—III. In conditional clauses εἰ (εἰ μή), and with the subj. often (sometimes w. the opt.) εἴ κεν, rarely w. ἄν, εἰ δ' ἂν ἐμοὶ τῖμὴν Πρίαμος Πριάμοιό τε παῖδεστῖ́νειν οὐκ ἐθέλωσιν, Il. 3.288. Conditions of which the conclusion is vague are sometimes regarded as interrogative, e. g. ἀναπεπταμένᾶς ἔχον ᾶ̓νέρες, εἴ τιν' ἑταίρωνἐκ πολέμου φεύγοντα σαώσειαν, they held the gates open, in case they might be able to save some fugitive, Il. 12.122; thus often εἴ που or εἴ πωσ, in the hope that, on the chance that, etc. —With other particles, εἰ καί, if also (or denoting concession, though), καὶ εἰ (οὐδ' εἰ, μηδ̓ εἰ), even if, denoting opposition; εἴ τε.. εἴ τε (sive.. sive), ὡς εἰ, ὡς εἴ τε, εἰ δή, εἴ περ, εἴ γε (q. v.); in εἰ δ' ἄγε (q. v.), εἰ is probably an interjection.