| Definition: | operation performed on a set for which an addition is defined, usually denoted by the minus symbol −, the result of which, for elements a and b of the set, is the unique element a − b, if it exists in the set, such that b + (a − b) = a Note 1 to entry: Subtraction is defined for integers and extended to other classes of numbers and to mathematical entities such as vectors and matrices, and also to quantities of the same kind. Note 2 to entry: The subtraction of entities a and b can be defined by a − b = a + (−b) where −b is the negative of b. Note 3 to entry: The subtraction of entities a and b is expressed by the words "a minus b".
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