Voice (grammar)

Diathesis (Ancient Greek διάθεσις diáthesis, German 'Aufstellung', 'Zustand', also direction of action) is a category of the verb in linguistics. It is based on the concept of semantic roles that a verb assigns to its complements. Diatheses regulate whether and in what form these participant roles given by the verb meaning appear in the sentence structure.

Diathesis thus starts from the level of meaning (semantics) of words and characterizes the mapping of these meaning relations into grammar. The grammatical forms of the verb which indicate a diathesis are called genus verbi (Latin-German: "genus (kind, gender) of the time word"). A genus verbi may also be ambiguous with respect to the diathesis it expresses. In some cases, however, the term genus verbi is also used in a broader sense, as synonymous with diathesis.

In the (Indo)European languages (including German), the best-known diathesis is that of the passive. In typologically different languages, other diatheses may dominate, e.g. the medium in Greek and Indo-European, the antipassive in ergative languages, or even the causative.

Examples from German

Examples from German will clarify the connections. The following seven example sentences express more or less the same facts:

1. Jörg plants Anne shrubs in the garden.
2. Anne is planted shrubs in the garden by Jörg.
3. Jörg plants Anne the garden with shrubs.
4. The garden is planted with shrubs by Anne of Jörg.
5. Anne has Jörg plant shrubs in the garden.
6. Anne has Jörg plant the garden with shrubs.
7. Anne has Jörg plant shrubs in her garden.

The difference in content between the sentences is that the first four do not explicitly state that the planting is done at Anne's suggestion, and the fifth and sixth do not explicitly state to whom the shrubs are planted in the garden. Both will often be inferred from the context. To a certain extent the sentences are interchangeable; which one to use will depend, among other things, on what has been the subject before, what is already known about it, and what is to be communicated anew.

The semantic (meaning) role played by Anne, Jörg, the garden and the bushes is the same in all sentences (not quite in the case of Anne's double role as principal and beneficiary). Nevertheless, the syntactic role, i.e. the grammatical means by which the connection of a noun (noun, name, pronoun) to the verb is established in each case, for the same noun depends on the exact form of the verb and on the use of auxiliary verbs - in particular, any of the four nouns can become the subject of the sentence. In the following table, each sentence is in a column (in the second sentence in a different word order), and for each word on the far left is the syntactic role.

The verb forms in the heading line of the table are diatheses of the same verb "to plant". The ones that occur here are:

• Active: the base form of the verb, often describing an active action, here "planting".
• Passive: the form of the verb in which the object of the action becomes the subject, here "to be planted".
• Applicative: the form of the verb in which a noun connected with a preposition becomes the object, here "to plant".
• Causative: the form of the verb in which the principal of an action becomes the subject, the old subject becomes the object, here "to let plant".

As you can see from the last examples, these shapes can also be combined.

Diatheses are formed - also in other languages - mainly in three ways:

• by morphological change of the verb: in German the prefix "be-" for the applicative; vowel change for some causatives ("setzen" from "sitzen", "tränken" from "trinken", "heften" from "haften" etc.)
• by using auxiliary verbs: in German, for example, "werden" for the passive and "lassen" for the causative.
• by using reflexive constructions even where someone or something is not acting on itself (German examples below)

Especially in the case of morphologically realized diatheses, the derived verb form often takes on a life of its own and acquires divergent meanings: to lead is not the same as to cause to drive (but when driving a vehicle it is), to blast is not the same as to cause to jump (but the blasted rock acquires jumps), and to fell, to waste, to flood and to suckle are only special cases of to cause to fall, to disappear, to swim and to suckle. One may own a land on which one sits (is settled) and commit a path on which one walks, but how can one literally own an account or commit a crime? In such cases, the formation mechanism of diathesis is still discernible, but the semantic context has been partially or completely lost.

Even in diatheses formed with auxiliary verbs or reflexive pronouns, the exact meaning is not always the same in the same syntactic construction. Compare, for example:

• have the secretary write a letter (order)
• allow (permit) the traveller to cross the border
• leave the hitchhiker at the side of the road (continue to do so)

or:

• he washes himself (the object is the doer himself)
• they meet (each other)
• the group meets (the members each other)
• the rain barrel fills up (but does nothing)
• he is ashamed (only used reflexively)

For these reasons it is necessary to distinguish the diathesis itself, i.e. the distribution of roles of the agents, the treated, the beneficiaries, the victims, the principals, etc., from its morphological or syntactic realization. The latter is then called the genus verbi (literally: the gender of the verb), especially in the case of morphological realization.

In a language, a genus verbi can be fully productive, i.e. applied to all verbs, always realizing the expected diathesis, or only partially, i.e. covering only some verbs or producing a wider range of possible diatheses. Above all, the passive is fully productive in many languages for transitive verbs - in German also for intransitive ones. The more productive a genus verbi is in a language, the more likely it is to be considered just another form of the underlying verb, thus not listed separately from the base form in dictionaries. The morphologically formed causatives and applicatives in German, on the other hand, are taken to be verbs in their own right, with their own dictionary entries.

Diathesis and valence alternation

The diathesis is a special case of the valence alternation or valence operation. While in diathesis only agent and patiens play a role, generally in valence operations there are also other roles (co-players). In the first example (active) there is a two-valued valence frame, in the passivized example there is only one obligatory actant, the prepositional phrase of Paul can also be omitted without the sentence becoming ungrammatical (The car is washed). Passivization is thus a means of valence reduction.