The additive inverse of a number is the value that, when added to the original number, results in zero. For example, the additive inverse of 5 is -5, because 5 + (-5) = 0. This concept is essential in mathematics, particularly in solving equations and understanding properties of numbers. In general, every real number has an additive inverse. For any number x, its additive inverse is represented as -x. This relationship helps in simplifying expressions and balancing equations, making it a fundamental concept in algebra and arithmetic.