According to the ending of the verb-stem, ω-verbs are termed:
1. Vowel (or pure) verbs:
a. Not contracted: those that end in υ or ι, as λύ_-ω
b. Contracted: those that end in α, ε, ο, as τι_μῶ
2. Consonant verbs, as:
Liquid or nasal verbs: δέρ-ω
Verbs ending in a stop (or mute), as ἄγ-ω
N.—Verbs ending in a stop consonant are called labial, dental, or palatal verbs. Consonant verbs do not retain the final consonant of the stem unchanged in all their forms. The final consonant may be assimilated to a following consonant, or may form with it a double consonant.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].