---
tag: 0RCQZ36MME
kind: concept
name: Indicator function
aliases: [characteristic-function]
msc: ["03E20"]
sources:
  - url: https://en.wikipedia.org/wiki/Indicator_function
    locator: lead section
same_as:
  wikidata: Q371983
  wikipedia: Indicator function
---

## Summary

The indicator function of a subset takes the value $1$ on the subset and the value $0$ outside it.