The third weak conjugation is characterized by the suffix PIE *-oi- > PGmc *-ai- added to the verbal root. The verbs of this class are typically not derived from other sources, and are generally durative or stative (see Section 40). For example, WG þuláiþ 'puts up with, endures' (compare also Old High German dolēt), WG siláiþ 'is silent', WG þaháiþ 'is silent' (compare Old High German dagēt).

The verb haban 'to have' serves to illustrate the forms of class iii weak verbs. The forms are as follows.

The origin of the present forms is unclear. Some scholars propose PIE *kapēti or *kapējéti, though this is less likely than proposing a PIE middle ending *kap-oi. This was then extended by the third singular ending *-ti: *kap-oi > *kap-oi-ti > WG habáiþ. Such a middle construction is also consonant with the stativity of many of the verbs of this class.