An unergative verb is an intransitive verb distinguished semantically by having an agent argument, or that treats the argument like the ergative argument of a transitive verb. For example, in English, run, talk and resign are unergative verbs, and fall and die are unaccusative verb.Lexicon
Some languages treat unergative verbs distinctly from other intransitives in morphosyntactic terms. For example, in some Romance languages, such verbs use different auxiliaries when forming the compound tenses.
Besides the above, unergative verbs differ from unaccusative verbs in that, in some languages, they can be passivized to a limited extent.
In Dutch for example, unergatives take hebben (to have) in the perfect tenses:
Ik telefoneer – ik heb getelefoneerd. "I call (by phone). – I have called."In such cases, a transition to an impersonal passive construction is possible using the adverb er (that functions as a dummy subject) and the passive auxiliary worden:
Er wordt door Jan getelefoneerd. "*There is by Jan telephoned." (i. e. "A telephone call by Jan is going on.")By contrast, ergative verbs take zijn ("to be") in the perfect tenses:
Het vet stolt – het vet is gestold "The grease solidifies – The grease has solidified."In that case, no passive construction with worden is possible. In other words, unergatives are truly intransitive, but ergatives are not.