Let L {\displaystyle {}L} and M {\displaystyle {}M} denote sets. A mapping F {\displaystyle {}F} from L {\displaystyle {}L} to M {\displaystyle {}M} is given by assigning, to every element of the set L {\displaystyle {}L} , exactly one element of the set M {\displaystyle {}M} . The unique element which is assigned to x ∈ L {\displaystyle {}x\in L} , is denoted by F ( x ) {\displaystyle {}F(x)} . For the mapping as a whole, we write
