Verbs in -μι usually have no thematic vowel between the tense-stem and the personal endings in the present system (except in the subjunctive). The name “μι-conjugation,” or “non-thematic” conjugation,” is applied to all verbs which form the present and imperfect without the thematic vowel.718
Of verbs ending in -μι the following tenses are inflected according to the μι-conjugation (except in the subjunctive): all non-thematic presents and imperfects; all aorists passive; all perfects and pluperfects middle; those second aorists active and middle in which the tense-stem does not end with the thematic vowel; one verb (ἵστημι) in the second perfect and pluperfect active.719
Certain tenses of verbs ending in -μι in the first person present indicative active, or in -μαι in the present middle (and passive) when not preceded by the thematic vowel, are inflected according to the ω-conjugation. These tenses are: all futures, all first aorists active and middle, most perfects and pluperfects active, and all subjunctives. Verbs in -νυ_μι regularly inflect the subjunctive and the optative according to the ω-conjugation. Furthermore, the 2 sing. in the present and 2 and 3 sing. in the imperfect active of certain verbs, and some other forms, follow the ω-conjugation ( cross746).720
Verbs in -μι add the endings directly either to the verb-stem (here a root) or after the suffixes νυ or νη. Hence three classes are to be distinguished.
A. Root class; as φη-μί
N.—Two verbs have verb-stems ending in a consonant: εἰμί
B. -νυ- class; as δείκ-νυ_-μι
C. A few verbs, mainly poetical, add να-, νη-; as σκίδ-νη-μι σκίδ-ναμεν
Deponent verbs without the thematic vowel are inflected according to the μι-conjugation.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].