An inverse element in a mathematical set is an element that, when combined with another element using a given binary operation, results in the identity element of that operation. This concept is fundamental in structures like groups, where every element must have an inverse to satisfy the group axioms.
Associativity is a property of certain binary operations that indicates the grouping of operands does not affect the result. This property is crucial in mathematics and computer science for optimizing computations and ensuring consistency in operations like addition and multiplication.