The case of a noun

In grammar, the case of a noun or pronoun is an inflectional form that indicates its grammatical function in a phrase, clause, or sentence. For example, a pronoun may play the role of subject ("I kicked the ball"), of direct object ("John kicked me"), or of possessor ("It is my ball"). Languages such as Ancient Greek, Latin, and Sanskrit had ways of altering or inflecting nouns to mark roles which are not specially marked in English, such as the ablative case ("John kicked the ball away from the house") and the instrumental case ("John kicked the ball with his foot"). In Ancient Greek those last three words would be rendered tōi podi (τῷ ποδί), with the noun pous (πούς, foot) changing to podi to reflect the fact that John is using his foot as an instrument (any adjective modifying "foot" would also change case to match). As a language evolves, cases can merge (for instance in Ancient Greek genitive and ablative have merged as genitive), a phenomenon formally calledsyncretism.

Usually a language is said to "have cases" only if nouns change their form (decline) to reflect their case in this way. Other languages perform the same function in different ways. English, for example, uses prepositions like "of" or "with" in front of a noun to indicate functions which in Ancient Greek or Latin would be indicated by changing (declining) the ending of the noun itself.

More formally, case has been defined as "a system of marking dependent nouns for the type of relationship they bear to their heads."Cases should be distinguished from thematic roles such as agent and patient. They are often closely related, and in languages such as Latin several thematic roles have an associated case, but cases are a morphological notion, while thematic roles are a semantic one. Languages having cases often exhibit free word order, since thematic roles are not dependent on position in a sentence.

Etymology

In many European languages, the word for "case" is cognate to the English word, all stemming from the Latin casus, related to the verb cadere, "to fall", with the sense that all other cases have fallen away from the nominative. Its proto-Indo-European root is *k^ad-1 .

Similarly, the word for "declension" and its many European cognates, including its Latin source declinatio come from the root *k^lei- , "to lean".