In grammar, an intransitive verb is an action verb that takes no object. Although there is some dispute over whether or not a linking verb is intransitive, many do not consider it an intransitive verb. Examples of intransitive verbs include:

• I slept.
• He died.
• She runs.

See also transitive verb and ditransitive verb.

There are languages that mark verbs for their transitivity, such that the verb in "I ate" and "I ate a fish" would have different affixes. In addition, ergative verbs generally take complementizers, while normal intransitive verbs can take prepositional phrases. Thus:

• He thought that you were ill.
• She runs through the woods.

But not

• He thought through the woods.
• She runs that you were ill.

Intransitive verbs can be either alternating or non-alternating. Alternating intransitive verbs have a transitive counterpart, whereas non-alternating intransitive verbs do not, examples include the following: Alternating verbs:

• The cup broke. I broke the cup.
• The seasons changed. I changed the channel.
• I ate. I ate the cake.
• The ship sank. The collision sank the ship.

Non-alternating verbs:

• The box appeared.
• The car vanished.
• The man died.

Although logical inference may imply that a direct object is involved with the alternating intransitives, it is not part of the syntactic representation of the sentence, it is either part of the discourse context, the nature of the verb, or both, compare the following:

• The ship sank.
• The ship was sunk.

The first sentence is inherently agentless, its deep structure does not and can not contain one. The second sentence, on the other hand, is a passive sentence, in which the subject is merely omitted and can be added using a by-phrase, as illustrated below this operation yields an ungrammatical sentence for the intransitive version of the verb, whilst it is perfectly acceptable for the transitive version.

• The ship sank by the opposition.
• The ship was sunk by the opposition.