Lexical semantics
Intransitive verbs: unaccusative versus unergative
### Intransitive verbs: unaccusative versus unergative

The unaccusative hypothesis was put forward by David Perlmutter in 1987, and describes how two classes of intransitive verbs have two different syntactic structures. These are [unaccusative verbs](/wiki/Unaccusative_verb "Unaccusative verb") and [unergative verbs](/wiki/Unergative_verb "Unergative verb").Lappin, S. (Ed.). (1996\). Handbook of contemporary semantic theory. Oxford, UK: Blackwell Publishers. These classes of verbs are defined by Perlmutter only in syntactic terms. They have the following structures underlyingly:

* unaccusative verb: \_\_ \[VP V NP]
* unergative verb: NP \[VP V]

The following is an example from English:

| ``` (2)  ```  **Unaccusative**  ```     a.  ```  *Mary fell.*Loporcaro, M. (2003\). The Unaccusative Hypothesis and participial absolutes in Italian: Perlmutter’s generalization revised. Rivista di Linguistica/Italian Journal of Linguistics, 15, 199\-263\. **Unergative**  ```     b.  ```  *Mary worked.* |
| --- |

In (2a) the verb underlyingly takes a direct object, while in (2b) the verb underlyingly takes a subject.


How many classes of intransitive verbs exist according to the unaccusative hypothesis?