case¹ (kās)

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[Middle English cas, from Old French, from Latin cāsus, from past participle of cadere, to fall.]

noun 

1. An instance of something; an occurrence; an example: a case of mistaken identity. See synonyms at example
2. An occurrence of a disease or disorder: a mild case of flu.
3. A set of circumstances or a state of affairs; a situation: It may rain, in which case the hike will be canceled.
4. Actual fact; reality: We suspected the walls were hollow, and this proved to be the case.
5. A question or problem; a matter: It is simply a case of honor.
6. A situation that requires investigation, especially by a formal or official body.
7. Law
   1. An action or a suit or just grounds for an action.
   2. The facts or evidence offered in support of a claim.
8. A set of reasons or supporting facts; an argument: presented a good case for changing the law.
9. A person being assisted, treated, or studied, as by a physician, lawyer, or social worker.
10. Informal A peculiar or eccentric person; a character.
11. Linguistics
    1. In traditional grammar, a distinct form of a noun, pronoun, or modifier that is used to express one or more particular syntactic relationships to other words in a sentence.
    2. Case. In some varieties of generative grammar, the thematic or semantic role of a noun phrase as represented abstractly but not necessarily indicated overtly in surface structure. In such frameworks, nouns in English have Case even in the absence of inflectional case endings.

idioms

in any case

Regardless of what has occurred or will occur.

in case

If it happens that; if. As a precaution: took along an umbrella, just in case.

in case of

If there should happen to be: a number to call in case of emergency.

off (someone's) case

No longer nagging or urging someone to do something.

on (someone's) case

Persistently nagging or urging someone to do something.

case² (kās)

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[Middle English, from Norman French casse, from Latin capsa.]

noun 

1. A container; a receptacle: a jewelry case; meat-filled cases of dough.
2. A container with its contents.
3. A decorative or protective covering or cover.
4. A set or pair: a case of pistols.
5. The frame or framework of a window, door, or stairway.
6. The surface or outer layer of a metal alloy.
7. Printing A shallow compartmented tray for storing type or type matrices.

transitive verb: cased, cas·ing, cas·es. 

1. To put into or cover with a case; encase.
2. Slang To examine carefully, as in planning a crime: cased the bank before robbing it.