eitheror

Eitheror refers to a binary choice between two options. In normal usage, the phrase either … or connects two alternatives and signals that one of the two should be chosen. It is commonly written as either/or when used as a compound adjective or noun, for example in phrases like an either/or decision or an either/or situation.

In logic, the expression corresponds to the exclusive disjunction, often called XOR. A and B cannot both be true for the statement to hold. The standard truth-functional interpretation is true when exactly one of A or B is true; false when both are true or both are false. In contrast, inclusive or would allow the possibility that both options are true.

Usage notes reflect ambiguity in ordinary speech. While either A or B usually implies that only one option is appropriate, some contexts treat the choice as nonexclusive. Writers may choose either/or to emphasize the pair of alternatives, or simply use either … or in a sentence without implying exclusivity.

Forms and examples: The term can appear as either/or, either-or, or simply either or in prose. It also appears in titles and phrases, such as the 1997 album Either/Or by Elliott Smith, which uses the conventional capitalization and slash in its title.

See also: exclusive or, disjunction, logical OR, XOR.