subtraction, 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).
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