By case we understand systematic differences in the form of nominal and adjectival predicates, corresponding (though not in a one-to-one way) to functional differences of the terms in which they occur. We thus take “case” in the traditional sense of morphological distinctions such as “nominative”, “accusative”, “dative”, etc. which have some manifestation in the surface form of linguistic expressions.
- Dik (1989), a pag.312

The main function of case distinctions is to express the underlying semantic functions of terms; some cases (typically nom/acc, or abs/erg) more primarily serve the expression of syntactic functions. In view of the fact that one case may typically express different functions, it is in general not possible to identify a “common meaning” for a given case. Languages have a certain freedom in distributing the different functions to be expressed over the limited number of cases available, and even closely related languages may differ in their particular division of labour among the cases. This may be understood by considering the functionality of case distinctions at a somewhat higher level of abstraction. We may then say that case distinctions serve two different purposes: • they have a “characterizing” function: they characterize a term as having one of a limited set of possible semantic or syntactic functions, and • they have a “distinguishing” function: they serve to keep terms with different semantic/syntactic functions apart in the structure of the clause.
- Dik (1989), a pag.313