In linguistic typology, tripartite alignment is a type of morphosyntactic alignment in which the main argument ('subject') of an intransitive verb, the agent argument ('subject') of a transitive verb, and the patient argument ('direct object') of a transitive verb are each treated distinctly in the grammatical system of a language. however, Wangkumara, Nez Perce, Ainu, Vakh Khanty, Semelai, Kalaw Lagaw Ya, Kham, and Yazghulami have all been claimed to demonstrate tripartite structure in at least some part of their grammar. While tripartite alignments are rare in natural languages, they have proven popular in constructed languages, notably the Na'vi language featured in 2009's Avatar.
In languages with morphological case, a tritransitive alignment typically marks the agent argument of a transitive verb with an ergative case, the patient argument of a transitive verb with the accusative case, and the argument of an intransitive verb with an intransitive case.
Tripartite, Ergative and Accusative systems
A tripartite language does not maintain any syntactic or morphological equivalence (such as word order or grammatical case) between the core argument of intransitive verbs and either core argument of transitive verbs. In full tripartite alignment systems, this entails the agent argument of intransitive verbs always being treated differently from each of the core arguments of transitive verbs, whereas for mixed system intransitive alignment systems this may only entail that certain classes of noun are treated differently between these syntactic positions.
Types of tripartite systems
Languages may be designated as tripartite languages in virtue of having either a full tripartite morphosyntactic alignment, or in virtue of having a mixed system which results in tripartite treatment of one or more specific classes of nouns.
In the above example, the intransitive case in (a) is glossed NOM, in accordance with Breen's original transcription. Across (1), we see differential case suffixes for each of intransitive (NOM), ergative (ERG), and accusative (ACC) case.
The same tripartite distinction is clear in the pronominal system:
In the above examples, we see the first person singular pronoun taking different forms for each of the S, A, and O arguments (marked NOM, ERG and ABS respectively), indicating the tripartite alignment in pronominal morphology.
Syntactic surveys of Wangkumara suggest this is generally true of the language as a whole. An example of the latter would be Nez Perce, which lacks ergative marking in the first and second person.
In the above examples, (2a) demonstrates the intransitive case marking (here coded as NOM), while (2b) demonstrates differential ergative and accusative markings. Thus, Nez Perce demonstrates tripartite differentiations in its third person morphology.
In Ainu, only first person inclusive and fourth person (first person plural exclusive / logographical / indefinite / etc.) display tripartite alignment as shown in the table.
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|+ Morphosyntactic alignment in Ainu