additive inverse	Any two numbers whose sum is zero, such as 3 and -3, because 3 + (-3) = 0.
inverse operations	A mathematical operation that can reverse or “undo” another operation. Addition and subtraction are inverse operations. Multiplication and division are inverse operations.
opposite	An opposite of a number is the number with the opposite sign, but same absolute value. For example, the opposite of 72 is -72. A number plus its opposite is always 0.
real numbers	All rational or irrational numbers.