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 that 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
