Herbert Weir Smyth, A Greek Grammar for Colleges

a. The present and past tenses of the indicative without ἄν express a fact or the assumption of a fact. The future indicative is used to denote purpose, present intention, or an intended result.

b. The indicative with ἄν denotes unreality.

c. The subjunctive with ἄν expresses a possible or supposed fact in future time or a generality in present time. The subjunctive without ἄν is used in indirect questions (1805 b).

d. The optative without ἄν expresses a wish, a possibility less distinctly conceived, or a generality in past time.

e. The optative with ἄν is potential, and is used either in conditional relative clauses with an optative in the main clause, or alone, as ““μἴ ἔστιν ἐλπίς, ᾗ μόνῃ σωθεῖμεν ἄν” there is one hope by which alone we may be saved” E. Hel. 815.

f. The imperative occurs in relative clauses (1842, 2553).

g. The infinitive occurs in relative clauses in indirect discourse (2631).

THE USE OF THE MOODS IN CERTAIN RELATIVE CLAUSES