A condition is a supposition on which a statement is based. A conditional sentence commonly consists of two clauses:
The protasis: the conditional, or subordinate, clause, expressing a supposed or assumed case (
The apodosis: the conclusion, or principal clause, expressing what follows if the condition is realized. The truth or fulfilment of the conclusion depends on the truth or fulfilment of the conditional clause.
a. The protasis has its name from πρότασις, lit.
The protasis usually precedes, but may follow, the apodosis.2282
The protasis is introduced by εἰ
a. Homer has also αι', which is an Aeolic (and Doric' form.2283
With the subjunctive mood, ει' commonly takes ἄν (Epic εἴ κε or εἴ κεν, not ἐά_ν).
a. There are three forms, ἐά_ν, ἤν, ἄ_ν. ἐά_ν is the ordinary form in Attic prose and inscriptions; ἤν appears in Ionic and in the older Attic writers (the tragic poets and Thucydides); ἄ_ν, generally in the later writers (sometimes together with ἐά_ν), very rarely in Attic inscriptions. In Plato ἄ_ν is commoner than ἐά_ν. Xenophon has all three forms.
b. ἤν is from εἰ ἄν, ἄ_ν from η' (another form of εἰ) + ἄν. The etymology of ἐά_ν is uncertain: either from η' ἄν or from εἰ ἄ_ν.
The particle ἄν is used in the apodosis: (1) with the optative, to denote possibility (cp. cross1824); (2) with the past tenses of the indicative, to denote either the non-fulfilment of the condition ( cross1786) or, occasionally, repetition ( cross1790).2285
The apodosis may be introduced by δέ or ἀλλά, less often by αὐτάρ. See under Particles. νῦν δέ
The negative of the protasis is μή because the subordinate clause expresses something that is conceived or imagined. μή negatives the conditional clause as a whole. On οὐ adherescent in protasis, see cross2698.
The negative of the apodosis is οὐ, in case the principal clause states the conclusion as a fact on the supposition that the protasis is true; μή, when the construction requires that negative ( cross2689).2287
The indicative, subjunctive, and optative moods, and the participle may stand in protasis and apodosis. The imperative and infinitive may be used in the apodosis. The future optative is not used in conditional sentences except in indirect discourse. The tenses in conditional sentences, except unreal conditions, have the same force as in simple sentences.2288
Instead of a formal conditional sentence the two members may be simply coördinated, the protasis having the form of an independent clause.
σμι_κρὸν λαβὲ παράδειγμα, καὶ πάντα εἴσει ἃ βούλομαι
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].