"Case" is a linguistics term regarding a manner of categorizing nouns, pronouns, adjectives, participles, and numerals according to their traditionally corresponding grammatical functions within a given phrase, clause, or sentence. In some languages, nouns, pronouns, adjectives, determiners, participles, prepositions, numerals, articles and their modifiers take different inflected forms, depending on their case. As a language evolves, cases can merge (for instance, in Ancient Greek, the locative case merged with the dative case), a phenomenon formally called syncretism.English has largely lost its inflected case system although personal pronouns still have three cases, which are simplified forms of the nominative, accusative and genitive cases. They are used with personal pronouns: subjective case (I, you, he, she, it, we, they, who, whoever), objective case (me, you, him, her, it, us, them, whom, whomever) and possessive case (my, mine; your, yours; his; her, hers; its; our, ours; their, theirs; whose; whosever). Forms such as I, he and we are used for the subject ("I kicked the ball"), and forms such as me, him and us are used for the object ("John kicked me").
Languages such as Ancient Greek, Armenian, Assamese, most Balto-Slavic languages, Basque, most Caucasian languages, most Dravidian languages, German, Icelandic, Japanese, Korean, Latin, Sanskrit, Tibetan (one of a few tonal languages), the Turkic languages and the Uralic languages have extensive case systems, with nouns, pronouns, adjectives, and determiners all inflecting (usually by means of different suffixes) to indicate their case. The number of cases differs between languages: Persian and Esperanto have two; modern English has three but for pronouns only; Modern Standard and Classical forms of Arabic have three; German and Icelandic have four; Romanian has five; Latin, Slovenian, Russian and Turkish each have at least six; Armenian, Czech, Latvian, Lithuanian, Polish, Serbo-Croatian, Slovak and Ukrainian have seven; Sanskrit and Tamil have eight; Estonian has 14; Finnish has 15; Hungarian has 18 and Tsez has 64 cases.Commonly encountered cases include nominative, accusative, dative and genitive. A role that one of those languages marks by case is often marked in English with a preposition. For example, the English prepositional phrase with (his) foot (as in "John kicked the ball with his foot") might be rendered in Russian using a single noun in the instrumental case or in Ancient Greek as τῷ ποδί (tôi podí, meaning "the foot") with both words (the definite article, and the noun πούς (poús) "foot") changing to dative form.
More formally, case has been defined as "a system of marking dependent nouns for the type of relationship they bear to their heads".