Inflectional forms that indicate the grammatical functions of nouns, pronouns and their modifiers (such as adjectives).

Case is a system of marking dependent nouns for the type of relationship they bear to their heads. Traditionally the term refers to inflectional marking, and, typically, case marks the relationship of a noun to a verb at the clause level or of a noun to a preposition, posposition or another noun at the phrase level.

Source: Case.