自動詞

About

In Japanese, intransitive verbs (自動詞じどうし) are characterized by their lack of a direct object. They also do not have an active agent or a "doer". Usually, intransitive verbs are accompanied by the が particle, although there are exceptions, and it can be omitted.

E.g. マイクが寝ねました。
"Mike slept."

The verb 寝ねる has no direct object, Mike doesn't "sleep" something, Mike simply "sleeps", and so we know this is an intransitive verb.

You can also verify whether or not a verb is intransitive by asking a "what" question. Since the question "What does Mike sleep?" doesn't make sense, we know 寝ねる is intransitive.

Summary

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  Intransitive verbs have no direct object

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  Intransitive verbs are often paired with the が particle