A function \(f\) from a set \(A\) to a set \(B\) (called the domain and the codomain, respectively) is a rule that describes how a value in the codomain \(B\) is assigned to an element from the domain...A function \(f\) from a set \(A\) to a set \(B\) (called the domain and the codomain, respectively) is a rule that describes how a value in the codomain \(B\) is assigned to an element from the domain \(A\).