Herbert Weir Smyth, A Greek Grammar for Colleges

a. Enclitics.—All the forms of φημί say, and εἰμί am, except φῄς and εἶ.

b. Imperatives.—(1) The second person sing. of the second aorist active imperative of five verbs is oxytone: εἰπέ say, ἐλθέ come, εὑρέ find, ἰδέ see, λαβέ take. Their plurals are accented εἰπέτε, ἐλθέτε, etc.; compounds have recessive accent: κάτειπε, ἄπελθε, ἔφευρε, παράλαβε.

(2) The second aorist middle (2 sing.) is perispomenon, as λαβοῦ, παραβαλοῦ, καθελοῦ.

c. Contracted verbs are only apparent exceptions: thus, e.g., τι_μᾷ for τι_μάει, δηλοῦσι for δηλόουσι, φιλεῖν for φιλέειν. So the subjunctive of the first and second aorist passive λυθῶ for λυθέω, φανῶ for φανέω; the optatives λυθεῖμεν from λυθέ-ι_-μεν, διδοῖμεν from διδό-ι_-μεν; the futures φανῶ for φανέω, φανοῖμι for φανέοιμι, φανεῖν for φανέειν, φανῶν for φανέων; λιπεῖν for λιπέεν; and the present and second aorist active and middle subjunctive of most μι-verbs, as τιθῶ for τιθέω, ἱστῶμαι, θῶμαι, perf. κεκτῶμαι. On διδοῦσι, τιθεῖσι, see 463 d.

N. 1.—In athematic optatives the accent does not recede beyond the diphthong containing -ι_-, the sign of the optative mood: ἱσταῖο, ἱσταῖμεν, ἱσταῖτο, διδοῖτο; and so in λυθεῖμεν, λυθεῖεν.

N. 2.—δύναμαι am able, ἐπίσταμαι understand, κρέμαμαι hang, ὀνίνημι profit, and ἐπριάμην bought (749 b, 750 b, 757 a) have recessive accent in the subjunctive and optative (δύνωμαι, ἐπίστωμαι, δύναιτο, κρέμαιτο).

d. Poetic forms sometimes fail to follow the rule, as ἐών being.