In general, intransitive verbs often involve weather terms, involuntary processes, states, bodily functions, motion, action processes, cognition, sensation, and emotion.
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."
In German, a sentence such as "The children sleep" can be made passive to remove the subject and becomes, "They are slept."
In many languages, there are "ambitransitive" verbs, which can occur either in a transitive or intransitive sense.
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.)
Compare the following (in Spanish): Sentences (3a) and (3b) show Romance pseudo-reflexive phrases, corresponding to English alternating intransitives.
Therefore, this is not the same as passive voice, where an intransitive verb phrase appears, but there is an implicit agent (which can be made explicit using a complement phrase): Other ambitransitive verbs (like eat) are not of the alternating type; the subject is always the agent of the action, and the object is simply optional.
In many languages, including English, some or all intransitive verbs can entail cognate objects—objects formed from the same roots as the verbs themselves; for example, the verb sleep is ordinarily intransitive, but one can say, "He slept a troubled sleep", meaning roughly "He slept, and his sleep was troubled."
In Pingelapese, a Micronesian language, intransitive verb sentence structure is often used, with no object attached.
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 preposition e 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.