1. an instance of a disease or disorder, usually at the level of the individual patient. In a borderline case, the symptoms resemble those of a disease or disorder but do not fully meet the criteria. See also proband.

2. a person who is the recipient of assistance (e.g., from a health care professional or lawyer).

3. a unit or observation to be analyzed, such as a nonhuman animal, a person, a group, an institution, an object, or any other entity from which a researcher gathers data.

4. a feature of certain languages in which the forms of nouns, pronouns, and (sometimes) adjectives are altered to indicate their syntactic relations with other words in a sentence. The role of case is most significant in highly inflected languages, such as German or Latin. In English, case endings are now restricted to the personal and possessive pronouns (I, me, mine, etc.) and to plural and possessive nouns (e.g., dogs, children, girl’s, girls’). See accusative; dative; genitive; nominative.

5. one of various categories used in case grammar to classify the elements of a sentence in terms of their semantic relations with the main verb. See agent; experiencer; instrumental; patient.