The bird flew.

In this sentence, the verb “flew” is intransitive because it does not require a direct object. The bird simply performed the action of flying without acting upon anything else.

Other examples of intransitive verbs include:

Laugh

Sit

Smile

Arrive

Occur

Yawn

Intransitive verbs describe actions or states that do not involve a direct object receiving the action. They contrasted with transitive verbs, which do require a direct object.