Unergative verb
An unergative verb is an intransitive verb that is distinguished semantically by having just an agent argument.
For example, in English, run, talk and resign are unergative verbs, and fall and die are unaccusative verbs. Even so, Dąbrowska noted that "to die" is an example of unaccusative mismatch.
Some languages treat unergative verbs differently from other intransitives in morphosyntactic terms. For example, in some Romance languages, such verbs use different auxiliaries when in compound tenses.
Besides the above, unergative verbs differ from unaccusative verbs in that in some languages, they can occasionally use the passive voice.
In Dutch, for example, unergatives take hebben in the perfect tenses:
In such cases, a transition to an impersonal passive construction is possible by using the adverb er, which functions as a dummy subject and the passive auxiliary worden:
By contrast, Dutch ergative verbs take zijn in the perfect tenses:
In that case, no passive construction with worden is possible. In other words, unergatives are truly intransitive, but ergatives are not.
