is the verb break in English.

:(1) broke .
:(2) broke.

In (1), the verb is transitive, and the subject is the agent of the action, i.e. the performer of the action of breaking the cup. In (2), the verb is intransitive and the subject is the patient 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 implicit middle voice. This has also been termed an anticausative

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