The numbers to add in an addition problem are called addends, summands or terms, while the answer to the problem is the sum. In the number sentence a+b=c, a and b are addends, while c is the sum.
Addition follows several rules of arithmetic. Addition is cumulative, so the order in which one adds the summands does not affect the sum. This is represented mathematically as a+b=b+a. Addition is associative when adding three or more addends, allowing the person adding the numbers to choose to add them in any order, so (a+b)+c=a+(b+c). Addition is considered the simplest of math operations, with young toddlers having the ability to learn to add small numbers.