Case exponence refers to the number of categories that a single (nominal or pronominal) formative can express in addition to its case­marking function.[1] If the formative expresses no additional functions, it is considered monoexponential (alternatively, analytic); such as agglutinative nominal inflection. More rarely, a formative may be polyexponential (cumulative or synthetic). In this case, external flexion (flexional nominal inflection) occurs. The simultaneous marking of categories is called coexponence. Coexponence often features the expression of number, possession or referentiality alongside case. (Referentiality is when case markers specify their host NP as topics or as having specific or definite reference, such as grammatical gender or class.) Verbal predicates, such as time, aspect, and mood (TAM), only very rarely occur as coexponential categories. Values other than NoCase and ExpMono require explanatory commentary.

Types:

NoCase: The language does not use nominal inflection (declension).

ExpMono: Formatives marking nouns and pronouns are monoexponential.

ExpNum: Formatives marking nouns and pronouns express not only case, but also number.

ExpPoss: Formatives marking nouns and pronouns express not only case, but also possession.

ExpRef: Formatives marking nouns and pronouns express not only case, but also reference.

ExpTAM: Formatives marking nouns and pronouns express not only case but at least one of the following: time, aspect, mood.

ExpMix: Formatives marking nouns and pronouns express mark not only case, but also number, reference, and at least two of the following categories: time, aspect, mood.

Multiple values may apply to a language. If one type is dominant, a slash (/) should separate the values, with the dominant value appearing first[2]; if neither is dominant, they should be listed with an ampersand (&) separating them. Explanation should be provided in the commentary.

[1] This should not be confused with the concepts of fusion, which is the relation between formatives (grammatical markers) and hosts (stems), or flexibility, which involves inflectional types and inflectional allomorphy.

[2] For example, ExpMono/ExpNum would indicate that the vast majority of cases are monoexponential, but one or two case endings can also express number.