In mathematics, a well-defined action that, when applied to any permissible combination of known entities, produces a new entity, e.g. , the process of addition in arithmetic--in adding 5 and 3 to obtain 8, the numbers 5 and 3 are the operands, the number 8 is the result, and the plus sign is the operator indicating that the operation performed is addition. See unary operation, binary operation.
... out with 27.6% under the age of 18, 6.2% from 18 to 24, 17.7% from 25 to 44, 36.0% from 45 to 64, and 12.5% who are 65 years of age or older. The median age is 44 ...