Case declension is the phenomenon in which morphological variants of nouns or noun phrases express case functions (the syntactic relationship between the noun or NP to another word, usually the verb).[1] Typologically, declension type is determined by the morphological behavior of the noun alongside a predicative verb.[2] Morphophonological alternation alone is not sufficient to mark case. [3]

Types:

NoCase: The language does not have case inflection.

NoNCase: Case is not marked on nouns.[4]

CaseNAff: Case is marked on nouns using suffixes.

CaseAffN: Case is marked on nouns using prefixes.

CaseTon: Case is marked on nouns using tonal differences.

CaseInflex: Case is marked on nouns using phonemic differences in the noun stem (internal flexion).[5]

CaseNClit: Case is marked on nouns using postpositional clitics (attaching to the end of the noun phrase).[6]

CaseClitN: Case is marked on nouns using prepositional clitics (attaching to the beginning of the noun phrase).

CaseInpozClit: Case is marked on nouns using inpositional clitics (attaching within the noun phrase, usually to the end of the first word of the phrase).

When a language displays more than one type, two values can be listed. If one type is statistically dominant, a slash (/) should separate the values, with the dominant value appearing first; if both types appear with equal frequency, the values should be listed with an ampersand (&) separating them.

[1] The use of adpositions (without morphological change in the noun) is a syntactic (not morphologic) expression of case function and thereby does not constitute case declension.

[2] In terms of the current parameter, it is irrelevant whether case marking is used to mark an argument or another adverbial function.

[3] For example, if case is marked using an affix, it is irrelevant whether this affix joins the core case or another variant of the noun stem. Variation in the noun stem is only relevant when it functions to express case.

[4] This value entails that case is marked on other word classes, such as pronouns. Details should be included in the commentary.

[5] If these variants occur at the beginning or end of the word, they should be examined to determine whether any morphological regularity can be observed (i.e., whether the same stem change occurs in a given environment). Cases of word-final stem change should be examined to determine whether they constitute stem-truncating affixation (in which grammatical functions are expressed primarily by prefixes or suffixes). If so, the language should be classified as CaseNAff or CaseAffN.

[6] Clitics phonologically attach to a syntactically determined word in the noun phrase. (For example, a clitic may always attach to the last word in the NP, which may not necessarily be the noun.)