In mathematics, the additive inverse of an element x, denoted -x,[1] is the element that when added to x, yields the additive identity, 0.[2] In the most familiar cases, this is the number 0, but it can also refer to a more generalized zero element.
In elementary mathematics, the additive inverse is often referred to as the opposite number.[3][4] The concept is closely related to subtraction[5] and is important in solving algebraic equations.[6] Not all sets where addition is defined have an additive inverse, such as the natural numbers.[7]