The mediopassive voice is a grammatical voice that subsumes the meanings of both the middle voice and the passive voice.
Languages of the Indo-European family (and many others) typically have two or three of the following voices: active, middle, and passive. "Mediopassive" may be used to describe a category that covers both the middle (or "medium") and the passive voice. In synchronic grammars, the mediopassive voice is often simply termed either "middle" (typical for grammars of e.g. Ancient and Modern Greek) or "passive" (typical for grammars of e.g. modern Danish).
In the oldest Indo-European languages, the distinction active/middle was the most important, whereas the development in later languages has generally been to replace the old distinction with (or to reinterpret it as) an active/passive distinction (e.g. modern English: to tease / to be teased).[1] The Proto-Indo-European language itself is typically reconstructed as having two voices, active and mediopassive, where the middle-voice element in the mediopassive voice was dominant. Ancient Greek also had a mediopassive in the present, imperfect, perfect, and pluperfect tenses, but in the aorist and future tenses the mediopassive voice was replaced by two voices, one middle and one passive. Only Modern Greek and Albanian retain mediopassive in all tenses.
A number of Indo-European languages have developed a new middle or mediopassive voice. Often this derives from a periphrastic form involving the active verb combined with a reflexive pronoun. This development happened independently in the Romance languages, the Slavic languages, and the North Germanic (Scandinavian) languages. North Germanic languages, and East Slavic languages, have fused the reflexive with the verb to form a new synthetic conjugation, whereas in the Romance languages the reflexive mostly remains separate.
The mediopassive can have many meanings depending on the context of the sentence.
A few examples of unaccusative verbs in English with meanings similar to a mediopassive:
Spanish is an example of a modern language with a mediopassive voice, normally indicated by the use of a reflexive pronoun. This can variously have a middle-voice meaning (subject acting onto itself, or for its own benefit) or a passive-voice meaning (something acts onto the subject).
An example sentence is Spanish; Castilian: El padre se enojó al ver a su hijo romper la lámpara. The English translation is "The father became angry upon seeing his son break the lamp." The verb Spanish; Castilian: se enojó is said to be mediopassive because it comprises the reflexive pronoun Spanish; Castilian: se and the simple verb Spanish; Castilian: enojó, which together literally mean "angered himself." This would be literally translated "The father angered himself upon seeing his son break the lamp."Pragmatics quickly rejects the middle-voice meaning for the intended mediopassive-voice meaning, translated above as "got angry," because the middle-voice is rarely used. Many intransitive Spanish verbs behave that way: Spanish; Castilian: me caí, I fell; Spanish; Castilian: me cansé, I became tired.
Serbo-Croatian and other Slavic languages are very similar in this respect to Spanish, employing the same constructs with the passive/reflexive particle se: Otac se razljutio kad je njegov sin razbio svjetiljku. This would be again literally translated "The father angered himself when his son broke the lamp." Similar constructs are Svjetiljka se razbila "The lamp broke" and Vrata su se zatvorila "The door closed." However, not all verbs permit such use.
The (medio)passive is used when one is unable or does not want to express the actor: Čaša se razbila "The glass broke", implying it "just happened", almost "on its own".
The mediopassive is found in some contemporary Scandinavian languages like Danish, Swedish, and Norwegian (whereas for example Icelandic keeps up a formal distinction between the middle and the passive).
The examples below are from Danish, but the situation is the same in Swedish and Norwegian. The passive use of the Danish mediopassive is probably predominant, but the medial use is quite frequent as well. Here are examples of sub-categories of the middle voice.
Classical Armenian had a mediopassive form that was marked by changing the verb's thematic vowel instead of with a unique conjugation like in other Indo-European languages. Modern Armenian has retained some of these active/mediopassive pairs, but the distinction between the two voices is no longer productive.