Middle voice

In syntax, the term middle voice is sometimes used for a kind of voice or valency-changing derivation that intransitivizes the base verb and has various semantic effects (often lexically conditioned) such as reflexive, reciprocal, anticausative, autocausative.

Comments
The use of this term in modern linguistics is derived from the middle voice in Greek, where traditionally three voices are distinguished: active voice, middle voice and passive voice.

Polysemy
The term middle is also used
 * for a kind of nonovert passive, especially in English (as in The book sells well), see middle (in English).

Survey article
The middle voice

Other languages
German Medium