subtractionsubtraction, fundamental operation of arithmetic; the inverse of addition. If a and b are real numbers (see number), then the number a  b is that number (called the difference) which when added to b (the subtractor) equals a (the subtrahend). In terms of addition the symbol  b is called the additive inverse of b with the property that the sum of a number and its inverse equals 0, or b +(  b ) = 0. It follows that  (  b ) = b. The subtraction of b from a is the same as the addition of a and the inverse of b, or a  b = a +(  b ); e.g., when a = 10 and b = 5, then 10  5 = 10+(  5). The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved. More on subtraction from Fact Monster:
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