“case: Inflectional category, basically of nouns, which typically marks their syntactic function in relation to other parts of a sentence. E.g, in Latin vidi puellam ‘I saw a girl,’ puellam ‘(a) girl’ has the ending of the accusative case (puella-m), which marks it as the object of the verb (vidi ‘I-saw’).
Thence of various more abstract constructs. Thus the function of Mary in I saw Mary is like that of puellam in the example from Latin. Therefore, it too is traditionally ‘accusative,’ in opposition to the same word as a ‘nominative,’ in Mary saw me. Hence abstract cases, posited in principle in all languages, regardless of whether they are realized, as in languages such as Latin, by inflections.”
Excerpted from: Matthews, P.H., ed. The Oxford Concise Dictionary of Linguistics. New York: Oxford University Press, 2014.
Mark's Text Terminal 