Definition n. Let \(A\)A and \(B\)B be sets. A map is a set \(\varphi \subseteq\) \(A \times B\)A B such that for each \(a \in A\)a A there is exactly one \(b \in B\)b B with \(\left( a, b \right) \in \varphi\)( a, b ) \varphi.
Definition n. Let \(A\)A and \(B\)B be sets. A map is a set \(\varphi \subseteq\) \(A \times B\)A B such that for each \(a \in A\)a A there is exactly one \(b \in B\)b B with \(\left( a, b \right) \in \varphi\)( a, b ) \varphi.