Ingrammar, anintransitive verb is a verb, aside from anauxiliary verb, whose context does not entail a transitiveobject. That lack of an object distinguishes intransitive verbs fromtransitive verbs, which entail one or more objects. Additionally, intransitive verbs are typically considered within a class apart frommodal verbs anddefective verbs.

In the following sentences, verbs are used without adirect object:

• "Riversflow."
• "Isneezed."
• "My dogran."
• "Waterevaporates when it's hot."
• "You'vegrown since I last saw you!"
• "I wonder how long it will be until I see you again after Imove."

The following sentences containtransitive verbs (they entail one or more objects):

• "Wewatcheda movie last night."
• "She'smakingpromises."
• "When I said that, my sistersmackedme."
• "Santagavemea present."
• "He continuouslyclickedhis pen and it was incredibly annoying to me."

Some verbs, calledambitransitive verbs, may entail objects but do not always require one. Such a verb may be used as intransitive in one sentence, and as transitive in another.

Intransitive		Transitive
"It israining."		"It israiningcats and dogs."
"When he finished the race, hevomited."		"When he finished the race, hevomited uphis lunch."
"Waterevaporates when it's hot."		"Heatevaporateswater."
"He's beensinging all day."		"He's beensingingbarbershop all day."
"You'vegrown since I last saw you."		"You'vegrowna beard since I last saw you!"

In general, intransitive verbs often involve weather terms, involuntary processes, states, bodily functions, motion, action processes, cognition, sensation, and emotion.^{[1]: 54–61}

Thevalency of a verb is related to transitivity. Where the transitivity of a verb only considers the objects, the valency of a verb considers all thearguments that correspond to a verb, including both the subject of the verb and all of the objects.

It is possible to change the contextually indicated sense of a verb from transitive to intransitive, and in so doing to change thevalency.

In languages that have apassive voice, a transitive verb in the active voice becomes intransitive in the passive voice. For example, consider the following sentence:

In this sentence, "hugged" is a transitive verb with "Mary" as its object. The sentence can be made passive with the direct object "Mary" as thegrammatical subject as follows:

This shift is calledpromotion of the object.

The passive-voice construction does not indicate an object. The passivized sentence could be continued with theagent:

It cannot be continued with a direct object to be taken by "was hugged". For example, it would be ungrammatical to write "Mary was hugged her daughter" to show that Mary and her daughter shared a hug.

Intransitive verbs can be rephrased as passive constructs in some languages. In English, intransitive verbs can be used in the passive voice when a prepositional phrase is included, as in, "The houses were lived in by millions of people."

Some languages, such asDutch, have animpersonal passive voice that lets an intransitive verb without a prepositional phrase be passive. InGerman, a sentence such as "The children sleep" can be made passive to remove the subject and becomes, "They are slept." However, no addition like "... by the children" is possible in such cases.

In languages withergative–absolutive alignment, the passive voice (where the object of a transitive verb becomes the subject of an intransitive verb) does not make sense, because the noun associated with the intransitive verb is marked as the object, not as the subject. Instead, these often have anantipassive voice. In this context, thesubject of a transitive verb is promoted to the "object" of the corresponding intransitive verb. In the context of anominative–accusative language like English, this promotion is nonsensical because intransitive verbs do not entail objects, they entail subjects. So, the subject of a transitive verb ("I" inI hug him) isalso the subject of the intransitive passive construction (I was hugged by him). But in an ergative–absolutive language likeDyirbal, "I" in the transitiveI hug him would involve theergative case, but the "I" inI was hugged would involve theabsolutive, and so by analogy the antipassive construction more closely resembles*was hugged me. Thus in this example, the ergative is promoted to the absolutive, and the agent (i.e.,him), which was formerly marked by the absolutive, is deleted to form the antipassive voice (or is marked in a different way, in the same way that in the English passive voice can still be specified as the agent of the action usingby him inI was hugged by him—for example, Dyirbal puts the agent in thedative case, andBasque retains the agent in the absolutive).

In many languages, there are "ambitransitive" verbs, which can occur either in a transitive or intransitive sense. For example, Englishplay is ambitransitive, since it is grammatical to sayHis son plays, and it is also grammatical to sayHis son plays guitar. English is rather flexible as regards verb valency, and so it has a high number of ambitransitive verbs; other languages are more rigid and require explicit valency changing operations (voice,causative morphology, etc.) to transform a verb from intransitive to transitive or vice versa.

In some ambitransitive verbs areergative verbs for which the alignment of the syntactic arguments to the semantic roles is exchanged. An example of this is the verbbreak in English.

(1)He brokethe cup.

(2)The cup broke.

In (1), the verb is transitive, and the subject is theagent of the action, i.e. the performer of the action of breaking the cup. In (2), the verb is intransitive and the subject is thepatient of the action, i.e. it is the thing affected by the action, not the one that performs it. In fact, the patient is the same in both sentences, and sentence (2) is an example of implicitmiddle voice. This has also been termed ananticausative.

Other alternating intransitive verbs in English arechange andsink.

In theRomance languages, these verbs are often calledpseudo-reflexive, because they are signaled in the same way asreflexive verbs, using theclitic particlese. Compare the following (inSpanish):

(3a)La taza se rompió. ("The cup broke.")

(3b)El barco se hundió. ("The boat sank.")

(4a)Ella se miró en el espejo. ("She looked at herself in the mirror.")

(4b)El gato se lava. ("The cat washes itself.")

Sentences (3a) and (3b) show Romance pseudo-reflexive phrases, corresponding to English alternating intransitives. As inThe cup broke, they are inherently without an agent; theirdeep structure does not and can not contain one. The action is not reflexive (as in (4a) and (4b)) because it is not performed by the subject; it just happens to it. Therefore, this is not the same aspassive voice, where an intransitive verb phrase appears, but there is an implicit agent (which can be made explicit using a complement phrase):

(5)The cup was broken (by the child).

(6)El barco fue hundido (por piratas). ("The boat was sunk (by pirates).")

Other ambitransitive verbs (likeeat) are not of the alternating type; the subject is always the agent of the action, and the object is simply optional. A few verbs are of both types at once, likeread: compareI read,I read a magazine, andthis magazine reads easily.

Some languages like Japanese have different forms of certain verbs to show transitivity. For example, there are two forms of the verb "to start":

(7)会議が始まる。 (Kaigi ga hajimaru., "The meeting starts.")

(8)会長が会議を始める。 (Kaichō ga kaigi o hajimeru., "The president starts the meeting.")

In Japanese, the form of the verb indicates the number of arguments the sentence needs to have.^[2]

Especially in some languages, it makes sense to classify intransitive verbs as:

• unaccusative when the subject is not an agent; that is, it does not actively initiate the action of the verb (e.g. "die", "fall").
  • Unaccusative verbs are typically used to show action or movement.
    • Examples:
      • Iarrived at the party around 8 o'clock.
      • Do you know what time the planedeparted?
      • The diseasespread to other towns.^[3]
      • Isat on the train.
      • I was in a car accident and the other personappeared out of no where.
• unergative when they have an agent subject.
  • Examples:
    • I am going toresign from my position at the bank.
    • I have torun six miles in the morning.
    • Johnate.^[4]

This distinction may in some cases be reflected in the grammar, where for instance differentauxiliary verbs may be used for the two categories.

In many languages, including English, some or all intransitive verbs can entailcognate objects—objects formed from the same roots as the verbs themselves; for example, the verbsleep is ordinarily intransitive, but one can say, "He slept a troubled sleep", meaning roughly "He slept, and his sleep was troubled."

InPingelapese, aMicronesian language, intransitive verb sentence structure is often used, with no object attached. There must be a stative or active verb to have an intransitive sentence. A stative verb has a person or an object that is directly influenced by a verb. An active verb has the direct action performed by the subject. Theword order that is most commonly associated with intransitive sentences issubject-verb. However,verb-subject is used if the verb is unaccusative or by discourse pragmatics.^[5]

InTokelauan, the noun phrases used with verbs are required when verbs are placed in groups. Verbs are divided into two major groups. Every verbal sentence must have that structure, which contains a singular noun phrase, without a preposition, called an unmarked noun phrase. Only if ako-phrase precedes the predicate, that rule may be ignored. The agent is what speakers of the language call the person who is performing the action of the verb. If a noun phrase that starts with the prepositione is able to express the agent, and the receiving person or thing that the agent is performing the action of the verb to is expressed by a singular noun phrase that lack a preposition, or unmarked noun phrase, the verb is then considered transitive. All other verbs are considered intransitive.^[6]

• Transitivity (grammatical category)
• Transitive verbs
• Verbs
• Ditransitive verbs
• Valency (linguistics)
• Morphosyntactic alignment
• English passive voice