- (analysis) A function which is equal to 1 for all points in its domain which belong to a given set, and is equal to 0 for all points in the domain which do not belong to that given set.
- (mathematics, probability theory) A complex function completely defining the probability distribution of a real-valued random variable
- The characteristic function of a set A is often represented as χA.
- (function equal to 1 on elements of a given set): indicator function
function equal to one on elements of a given set — see indicator function
a complex function completely defining a probability distribution