Case is a grammatical category whose value reflects the grammatical function performed by a noun or pronoun in a phrase, clause, or sentence. In some languages, nouns, pronouns and their modifiers take different inflected forms depending on what case they are in. English has largely lost its case system, although case distinctions can still be seen with the personal pronouns: forms such as I, he and we are used in the role of subject ("I kicked the ball"), while forms such as me, him and us are used in the role of object ("John kicked me").
Languages such as Ancient Greek, Latin, Sanskrit, Russian and Finnish have extensive case systems, with nouns, pronouns, adjectives and determiners all inflecting (usually by means of different suffixes) to indicate their case. A language may have a number of different cases (Latin and Russian each have at least six; Finnish has 15). Commonly encountered cases include nominative, accusative, dative and genitive. A role that one of these languages marks by case will often be marked in English using 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 tōi podi, meaning "the foot" with both words (the definite article, and the noun πούς pous, "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.":p.1 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 required to be marked by position in the sentence.
The English word case used in this sense comes from the Latin casus, which has the same meaning, and is related to the verb cadere, "to fall" (from the proto-Indo-European root *k^ad-1). The sense is that all other cases are considered to have "fallen" away, to various degrees, from the nominative. This picture is also reflected in the word declension, from Latin declinare, "to lean" (PIE root *k^lei-).
The equivalent to "case" in several other European languages also derives from casus, including cas in French, caso in Spanish and Kasus in German. The Russian word падеж padyezh and the Polish przypadek similarly contain the root meaning "fall". The Finnish equivalent is sija, which can also mean "position" or "support".
Indo-European languages 
While not very prominent in modern English, cases featured much more saliently in Old English and other ancient Indo-European languages, such as Latin, Ancient Greek, and Sanskrit. Historically, the Indo-European languages had eight morphological cases, though modern languages typically have fewer, using prepositions and word order to convey information that had previously been conveyed using distinct noun forms. Among modern languages, cases still feature prominently in most of the Balto-Slavic languages (except Macedonian and Bulgarian), with most having six to eight cases, as well as Icelandic, German and Modern Greek, which have four. In German, cases are mostly marked on articles and adjectives, and less so on nouns. In Icelandic, articles, adjectives, personal names and nouns are all marked for case, making it, among other things, the living Germanic language that could be said to most closely resemble Proto-Germanic.
The eight historical Indo-European cases are as follows, with examples either of the English case or of the English syntactic alternative to case:
- The nominative case indicates the subject of a finite verb: We went to the store.
- The accusative case indicates the direct object of a verb: The clerk remembered us.
- The dative case indicates the indirect object of a verb: The clerk gave us a discount. or The clerk gave a discount to us.
- The ablative case indicates movement from something, or cause: The victim went from us to see the doctor. and He was unhappy because of depression.
- The genitive case, which roughly corresponds to English's possessive case and preposition of, indicates the possessor of another noun: John's book was on the table. and The pages of the book turned yellow.
- The vocative case indicates an addressee: John, are you all right? or simply Hello, John!
- The locative case indicates a location: We live in China.
- The instrumental case indicates an object used in performing an action: We wiped the floor with a mop. and Written by hand.
All of the above are just rough descriptions; the precise distinctions vary from language to language, and are often quite complex. Case is based fundamentally on changes to the noun to indicate the noun's role in the sentence. This is not how English works, where word order and prepositions are used to achieve this.
Modern English has largely abandoned the inflectional case system of Indo-European in favor of analytic constructions. The personal pronouns of Modern English retain morphological case more strongly than any other word class (a remnant of the more extensive case system of Old English). For other pronouns, and all nouns, adjectives, and articles, grammatical function is indicated only by word order, by prepositions, and by the genitive clitic -'s.
Taken as a whole, English personal pronouns are typically said to have three morphological cases:
- The nominative case (subjective pronouns such as I, he, she, we), used for the subject of a finite verb and sometimes for the complement of a copula.
- The oblique case (object pronouns such as me, him, her, us), used for the direct or indirect object of a verb, for the object of a preposition, for an absolute disjunct, and sometimes for the complement of a copula.
- The genitive case (possessive pronouns such as my/mine, his, her(s), our(s)), used for a grammatical possessor. This is not always considered to be a case; see English possessive: Status of the possessive as a grammatical case.
Most English personal pronouns have five forms; in addition to the nominative and oblique case forms, the possessive case has both a determiner form (such as my, our) and a distinct independent form (such as mine, ours) (with the exceptions that these are not distinct for the third person singular masculine [his car, it is his] and that the third person singular neuter it does not have the possessive independent form); and they have a distinct reflexive or intensive form (such as myself, ourselves). The interrogative personal pronoun who exhibits the greatest diversity of forms within the modern English pronoun system having definite nominative, oblique, and genitive forms (who, whom, whose) and equivalently coordinating indefinite forms (whoever, whomever, and whosoever).
Though English pronouns can have subject and object forms (he/him, she/her), nouns show only a singular/plural and a possessive/non-possessive distinction (e.g., chair, chairs, chair's, chairs'). Note that chair does not change form between "the chair is here" (subject) and "I saw the chair" (direct object), a distinction made by word order and context.
Hierarchy of cases 
Cases can be ranked in the following hierarchy, where a language that does not have a given case will tend to not have any cases to the right of the missing case::p.89
- Nominative > accusative or ergative > genitive > dative > locative > ablative > instrumental > prepositional > others.
Case concord systems 
In the most common case concord system, only the final word (the noun) in a phrase is marked for case. This system appears in Turkic languages, Mongolian, Quechua, Dravidian languages, many Papuan languages, Indo-Aryan languages, and others. In Basque and various Amazonian and Australian languages, only the phrase-final word (not necessarily the noun) is marked for case. In many Indo-European, Balto-Finnic, and Semitic languages, case is marked on the noun, the determiner, and usually the adjective. Other systems are less common. In some languages, there is double-marking of a word as both genitive (to indicate semantic role) and another case such as accusative (to establish concord with the head noun).
Declension paradigms 
Languages with rich nominal inflection typically have a number of identifiable declension classes, or groups of nouns with a similar pattern of case inflection. While Sanskrit has six classes, Latin is traditionally said to have five declension classes, and Ancient Greek three declension classes.
In Indo-European languages, declension patterns may depend on a variety of factors, such as gender, number, phonological environment, and irregular historical factors. Pronouns sometimes have separate paradigms. In some languages, particularly Slavic languages, a case may contain different groups of endings depending on whether the word is a noun or an adjective. A single case may contain many different endings, some of which may even be derived from different roots. For example, in Polish, the genitive case has -a, -u, -ów, -i/-y, -e- for nouns, and -ego, -ej, -ich/-ych for adjectives. To a lesser extent, a noun's animacy or humanness may add another layer of complication.
An example of a Latin case inflection is given below, using the singular forms of the Latin term for "sailor," which belongs to Latin's first declension class.
- nauta (nominative) "[the] sailor" [as a subject] (e.g. nauta ibi stat the sailor is standing there)
- nautae (genitive) "the sailor's / of [the] sailor" (e.g. nomen nautae Claudius est the sailor's name is Claudius)
- nautae (dative) "to/for [the] sailor" [as an indirect object] (e.g. nautae donum dedi I gave a present to the sailor)
- nautam (accusative) "[the] sailor" [as a direct object] (e.g.nautam vidi I saw the sailor)
- nautā (ablative) "by/with/from/in [the] sailor" [in various uses not covered by the above] (e.g. sum altior nautā I am taller than the sailor).'
- nauta (vocative) "calling to/ addressing the sailor" (e.g. "gratias tibi ago, nauta" I thank you, sailor).
Grammatical case was analyzed extensively in Sanskrit. The grammarian Pāṇini identified six semantic roles or karaka, which are related to the seven Sanskrit cases (nominative, accusative, instrumental, dative, ablative, genitive, and locative), but not in a one-to-one way. The six karaka are:
- Agent (kartri, related to the nominative)
- Patient (karman, related to the accusative)
- Means (karaṇa, related to the instrumental)
- Recipient (sampradāna, related to the dative)
- Source (apādāna, related to the ablative)
- Locus (adhikaraṇa, related to the locative)
For example, consider the following sentence:
|from the tree||a leaf||to the ground||falls|
|"a leaf falls from the tree to the ground"|
Here leaf is the agent, tree is the source, and ground is the locus, the corresponding declensions are reflected in the morphemes -am -at and -au respectively.
The Tamil case system is analyzed in native and missionary grammars as consisting of a finite number of cases. The usual treatment of Tamil case (Arden 1942) is one where there are seven cases—the nominative (first case), accusative (second case), instrumental (third), dative (fourth), ablative (fifth), genitive (sixth), and locative (seventh). In traditional analyses there is always a clear distinction made between postpositional morphemes and case endings. The vocative is sometimes given a place in the case system as an eighth case, although vocative forms do not participate in usual morphophonemic alternations, nor do they govern the use of any postpositions. Modern grammarians however argue that this eight-case classification is coarse and artificial, and that Tamil usage is best understood if each suffix or combination of suffixes is seen as marking a separate case.
|First case||Nominative||Subject of sentence||[Zero]|
|Second case||Accusative||Object of action||-ai|
|Third case||Instrumental, Social||Means by which action is done (Instrumental), Association, or means by which action is done (Social)||-al, -out|
|Fourth case||Dative||Object to whom action is performed, Object for whom action is performed||(u)kku,(u)kkàka|
|Fifth case||Ablative of motion from||Motion from an animate/inanimate object||-il, -ininru, -iliruntu, -iruntu, -itattiliruntu|
|Sixth case||Genitive||Possessive||[Zero], -in, -utaiya, -inutaiya|
|Seventh case||Locative||Place in which, On the person of (animate) in the presence of||-il,itam|
|Eighth case||Vocative||Addressing, calling||e, a|
As languages evolve, case systems change. In Ancient Greek, for example, the genitive and ablative cases became combined, giving five cases, rather than the six retained in Latin. In modern Hindi, the Sanskrit cases have been reduced to two: a direct case (for subjects and direct objects) and an oblique case. In English, apart from the pronouns discussed above, case has vanished altogether except for the possessive/non-possessive dichotomy in nouns.
The evolution of the treatment of case relationships can be circular.:pp.167-174 Adpositions can become unstressed and sound like they are an unstressed syllable of a neighboring word. A postposition can thus merge into the stem of a head noun, developing various forms depending on the phonological shape of the stem. Affixes can then be subject to various phonological processes such as assimilation, vowel centering to the schwa, phoneme loss, and fusion, and these processes can reduce or even eliminate the distinctions between cases. Languages can then compensate for the resulting loss of function by creating adpositions, thus coming full circle.
Recent experiments in agent-based modeling have shown how case systems can emerge and evolve in a population of language users. The experiments demonstrate that language users may introduce new case markers in order to reduce the cognitive effort required for semantic interpretation, hence facilitating communication through language. Case markers then become generalized through analogical reasoning and reuse.
Linguistic typology 
- Nominative–accusative (or simply accusative): The argument (subject) of an intransitive verb is in the same case as the agent (subject) of a transitive verb; this case is then called the nominative case, with the patient (direct object) of a transitive verb being in the accusative case.
- Ergative–absolutive (or simply ergative): The argument (subject) of an intransitive verb is in the same case as the patient (direct object) of a transitive verb; this case is then called the absolutive case, with the agent (subject) of a transitive verb being in the ergative case.
- Ergative–accusative (or tripartite): The argument (subject) of an intransitive verb is in its own case (the intransitive case), separate from that of the agent (subject) or patient (direct object) of a transitive verb (which is in the ergative case or accusative case, respectively).
- Active–stative (or simply active): The argument (subject) of an intransitive verb can be in one of two cases; if the argument is an agent, as in "He ate," then it is in the same case as the agent (subject) of a transitive verb (sometimes called the agentive case), and if it's a patient, as in "He tripped," then it is in the same case as the patient (direct object) of a transitive verb (sometimes called the patientive case).
- Trigger: One noun in a sentence is the topic or focus. This noun is in the trigger case, and information elsewhere in the sentence (for example a verb affix in Tagalog) specifies the role of the trigger. The trigger may be identified as the agent, patient, etc. Other nouns may be inflected for case, but the inflections are overloaded; for example, in Tagalog, the subject and object of a verb are both expressed in the genitive case when they are not in the trigger case.
The following are systems that some languages use to mark case instead of, or in addition to, declension:
- Positional: Nouns are not inflected for case; the position of a noun in the sentence expresses its case.
- Adpositional: Nouns are accompanied by words that mark case.
With a few exceptions, most languages in the Finno-Ugric group make extensive use of cases. Finnish has 15 cases according to the traditional understanding (or up to 30 depending on the interpretation). However, only 12 are commonly used in speech (see Finnish noun cases). Estonian has 14 and Hungarian has 18.
The lemma form of words, which is the form chosen by convention as the canonical form of a word, is usually the most unmarked or basic case, which is typically the nominative, trigger, or absolutive case, whichever a language may have.
See also 
- Agreement (linguistics)
- Case hierarchy
- Differential object marking
- List of grammatical cases
- Verbal case
- Thematic relation
- Voice (grammar)
- Phi features
- Clackson (2007) p.91
- Blake, Barry J. Case. Cambridge University Press: 2001.
- Among Slavic languages, Bulgarian and Macedonian are exceptions.Slavic Languages on quickia.com
- Frank Beetham, Learning Greek with Plato, Bristol Phoenix Press, 2007.
- Amba Kulkarni and Peter Scharf (eds), Sanskrit Computational Linguistics: First and Second International Symposia Rocquencourt, France, October 29-31, 2007 and Providence, RI, USA, May 15-17, 2008, Revised Selected Papers, Volume 5402 of Lecture notes in artificial intelligence, Springer, 2009, ISBN 3-642-00154-8, pp. 64–68.
- Pieter Cornelis Verhagen, Handbook of oriental studies: India. A history of Sanskrit grammatical literature in Tibet, Volume 2, BRILL, 2001, ISBN 90-04-11882-9, p. 281.
- K. V. Zvelebil (1972). "Dravidian Case-Suffixes: Attempt at a Reconstruction". Journal of the American Oriental Society 92 (2): 272–276. doi:10.2307/600654. JSTOR 600654.
- Arden, A. H. 1942, repr. 1969. A Progressive Grammar of the Tamil Language. Madras: Christian Literature Society.
- Harold F. Schiffman (June 1998). "Standardization or restandardization: The case for "Standard" Spoken Tamil". Language in Society 27 (3): 359–385. doi:10.1017/S0047404598003030.
- R. S. McGregor, Outline of Hindi Grammar, Oxford University Press, 1972.
- Remi van Trijp, "The Evolution of Case Systems for Marking Event Structure". In: Steels, Luc (Ed.), Experiments in Cultural Language Evolution, Amsterdam: John Benjamins, 2012, p. 169-205.