Anticausative Verb

An anticausative verb is an intransitive verb that shows an event affecting its subject, while giving no semantic or syntactic indication of the cause of the event. The single argument of the anticausative verb (its subject) is a patient, that is, what undergoes an action. One can assume that there is a cause or an agent of causation, but the syntactic structure of the anticausative makes it unnatural or impossible to refer to it directly. Examples of anticausative verbs are break, sink, move, etc.

Anticausative verbs are a subset of unaccusative verbs. Although the terms are generally synonymous, some unaccusative verbs are more obviously anticausative, while others (fall, die, etc.) are not; it depends on whether causation is defined as having to do with an animate volitional agent (does "falling" means "being accelerated down by gravity" or "being dropped/pushed down by someone"? Is "old age" a causation agent for "dying"?).