case has 31 distinct synonyms spread across 15 of its 22 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a special set of circumstances
“in that event, the first possibility is excluded”
a comprehensive term for any proceeding in a court of law whereby an individual seeks a legal remedy
“the family brought suit against the landlord”
the actual state of things
“that was not the case”
a portable container for carrying several objects
“the musicians left their instrument cases backstage”
a person requiring professional services
“a typical case was the suburban housewife described by a marriage counselor”
a person who is subjected to experimental or other observational procedures; someone who is an object of investigation
“the subjects for this investigation were selected randomly”
a problem requiring investigation
“Perry Mason solved the case of the missing heir”
a statement of facts and reasons used to support an argument
“he stated his case clearly”
nouns or pronouns or adjectives (often marked by inflection) related in some way to other words in a sentence
a specific state of mind that is temporary
“a case of the jitters”
a specific size and style of type within a type family
(printing) the receptacle in which a compositor has his type, which is divided into compartments for the different letters, spaces, or numbers
“for English, a compositor will ordinarily have two such cases, the upper case containing the capitals and the lower case containing the small letters”
bed linen consisting of a cover for a pillow
“the burglar carried his loot in a pillowcase”
a glass container used to store and display items in a shop or museum or home
look over, usually with the intention to rob
“They men cased the housed”
Synonyms, antonyms and the broader and narrower relations for case come from Princeton University’s WordNet. Full sources and licences.