Unaccusative verb
An unaccusative verb is a special kind of intransitive verb, which is distinguished semantically by the fact that its subject does not actively initiate or is not actively responsible for the action of the verb; rather, it has properties which it shares with the direct object of a transitive verb (or better, with the grammatical subject of its passive counterpart). For example, in English, arrive, die and fall are unaccusative verbs (while run and resign are not).
Unaccusative verbs cannot be passivized, due to the fact that their subject is not a semantic agent. That is, it is ungrammatical to say *it is died or *I am coughed. In English, phrases like he is fallen are either formal/archaic perfectives, or can be explained by considering fallen an adjective, rather than a participle. This is immediately apparent by the fact that it is semantically absurd to have X is fallen by Y, where Y is an agent.
Besides the restrictions of passivization, some languages treat unaccusative verbs distinctly from other intransitives (unergative verbs) in morphosyntactical terms. That is, the difference between unaccusatives and other intransitives shows up in the verb word or phrase. In French and Italian, among other Romance languages, unaccusative verbs form their periphrastic perfect tenses using the equivalent of be, while all other verbs use the equivalent of have (as in English).
- French:
- J'ai regardé "I have looked"
- Je suis tombé "I am fallen" (unaccusative, meaning "I have fallen")
- Italian:
- Lui ha telefonato "He has phoned"
- Lui è arrivato "He is come" ("He has come")
In Romance languages that distinguish unaccusatives from other verbs, the participles used with be behave as if they were truly adjectives, and hence agree with the (maybe implicit) subject in number and gender. That is, Italian è arrivato shows that the subject is masculine and singular; a feminine subject would use (lei) è arrivata; and a plural masculine subject would use (loro) sono arrivati. The participles used with non-unaccusative verbs are invariable, as is the case of all participles in the other Romance languages when used for complex tenses.
References
- Lexicon of Linguistics (Utrecht institute of Linguistics)