Verbs in -ω fall into two main classes, distinguished by the last letter of the verb-stem:
1. Vowel verbs: a. Uncontracted verbs. b. Contracted verbs.
2. Consonant verbs: a. Liquid verbs. b. Stop (or mute) verbs.
N. Under 2 fall also (c) those verbs whose stems ended in ς or ϝ ( cross624).
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].