Direct–inverse alignment

The definition of a direct–inverse language is a matter under research, but it is widely understood to involve different grammar for transitive predications according to the relative positions of their "subject" and their "object" on a person hierarchy, which, in turn, is some combination of saliency and animacy specific to a given language. The direct construction is the unmarked one. The direct construction is used when the subject of the transitive clause outranks the object in the person hierarchy, and the inverse is used when the object outranks the subject.

The existence of direct–inverse morphosyntax is usually accompanied by proximate–obviative morphosyntax. The direct–inverse dimension subsumes the proximate–obviative dimension. Across languages, obviation almost always involves the third person (although second-person obviation is reported for some Nilo-Saharan languages), and the direct–inverse alternation is usually presented as being a way of marking the proximate–obviative distinction between two (or more) third-person arguments of a sentence. However, there are at least two languages with inverse systems, the Mesoamerican languages Zoque and Huastec, in which inverse morphosyntax is never used when both subject and object are third person but only when one of the arguments is third person, and the other is a speech act participant (SAP), the first or second person.