In linguistic typology, tripartite alignment is a type of morphosyntactic alignment in which the main argument of an intransitive verb, the agent argument of a transitive verb, and the patient argument of a transitive verb are each treated distinctly in the grammatical system of a language. This is in contrast with nominative-accusative and ergative-absolutive alignment languages, in which the argument of an intransitive verb patterns with either the agent argument of the transitive or with the patient argument of the transitive. Thus, whereas in English, "she" in "she runs" patterns with "she" in "she finds it", and an ergative language would pattern "she" in "she runs" with "her" in "he likes her", a tripartite language would treat the "she" in "she runs" as morphologically and/or syntactically distinct from either argument in "he likes her". Which languages constitute genuine examples of a tripartite case alignment is a matter of debate; however, Wangkumara, Nez Perce, Ainu, Vakh dialects of Khanty, Semelai, Kalaw Lagaw Ya, Kham, and Yazghulami have all been claimed to demonstrate tripartite structure in at least some part of their grammar. Tripartite alignments are rare in natural languages, although it has proven popular in constructed languages, notably including the fictional Na'vi language featured in the 2009 movieAvatar. 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 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. The arguments of a verb are usually symbolized as follows:
A = 'agent' argument of a transitive verb
O = 'patient' argument of a transitive verb
S = argument of an intransitive verb
The relationship between accusative, ergative, and tripartite alignments can be schematically represented as follows:
See morphosyntactic alignment for a more technical explanation. The term 'subject' has been found to be problematic when applied to languages which have any morphosyntactic alignment other than nominative-accusative, and hence, reference to the 'agent' argument of transitive sentences is preferred to the term 'subject'.
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.
Full tripartite systems
A full tripartite system distinguishes between S, A and O arguments in all classes of nominals. It has been claimed that Wangkumara has the only recorded full tripartite alignment system.
Example
Wangkumara consistently differentiates marking on S, A, and O arguments in the morphology, as demonstrated in example below: In the above example, the intransitive case in is glossed NOM, in accordance with Breen's original transcription. Across, we see differential case suffixes for each of intranstive, ergative, and accusative 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, indicating the tripartite alignment in pronominal morphology. Syntactic surveys of Wangkumara suggest this is generally true of the language as a whole. Hence, Wangkumara represents a case of a full tripartite alignment.
Mixed systems
More common than full tripartite systems, mixed system tripartite alignments either demonstrate tripartite alignment in some subsection of the grammar, or else lacks the ergative, the accusative, or both in some classes of nominals. An example of the former kind of mixed system may be Yazghulami, which exhibits tripartite alignment but only in the past tense. An example of the latter would be Nez Perce, which lacks ergative marking in the first and second person. The following examples from Nez Perce illustrate the intransitive-ergative-accusative opposition that holds in the third person: In the above examples, demonstrates the intranstive case marking, while demonstrates differential ergative and accusative markings. Thus, Nez Perce demonstrates tripartite differentiations in its third person morphology.
