Indicative.—The perfect middle is inflected by adding the primary middle endings directly to the tense-stem, herein agreeing with the μι-conjugation. The pluperfect adds the secondary middle endings. In vowel verbs the formation is simple, as in λέλυ-μαι, ἐλελύ-μην. But in consonant verbs, the consonant at the end of the stem comes into collision with the consonant at the beginning of the ending; hence certain euphonic changes described in 409. The periphrastic form occurs in the 3 pl. and sometimes in the 3 sing. ( cross599 d, e).
a. Stems in ν avoid the forms -ν-σαι, -ν-σο; thus, from φαίνω, instead of πέφανσαι, ἐπέφανσο the periphrastic πεφασμένος εἶ, ἦσθα were probably used.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].