In ergative languages
In ergative–absolutive languages, the absolutive is the case used to mark both the subject of an intransitive verb and the object of a transitive verb, in addition to being used for the citation form of a noun. It contrasts with the marked ergative case, which marks the subject of a transitive verb.
For example, in Basque the noun mutil ("boy") takes the bare singular article -a both as subject of the intransitive clause mutila etorri da ("the boy came") and as object of the transitive clause Irakasleak mutila ikusi du ("the teacher has seen the boy"), in which the subject bears the ergative ending -a-k.
In marked-nominative languages
In nominative–absolutive languages, also called marked-nominative languages, the nominative has a case inflection, while the accusative and citation form do not. The unmarked accusative/citation form may be called absolutive to clarify that the citation form is used for the accusative case role rather than for the nominative, which it is in most nominative–accusative languages.
In tripartite languages
In tripartite languages, both the agent and object of a transitive clause have case forms, ergative and accusative, whereas the agent of an intransitive clause is the unmarked citation form. This is occasionally called the intransitive case, but absolutive is also used and is perhaps more accurate, since it is not limited to core agents of intransitive verbs.
In accusative languages
In nominative–accusative languages, both core cases may be marked, but not infrequently only the accusative is. In such situations the term 'absolutive' would aptly describe the nominative, but the term is seldom used that way.