Definition:Characteristic Function (Set Theory)

Also known as
It is also known as the indicator function, and $\map {\chi_E} x$ denoted $\map {\mathbf 1_E} x$.

Some sources, in an attempt to apply consistency to the terminology, refer to this concept as a characteristic mapping, but this term appears to be rare.

Some sources use the symbol $\phi$ to denote a characteristic function.