---
tag: 0RBKKNH4GV
kind: concept
name: Focus of a conic
aliases: [focus]
msc: [51N20]
sources:
  - url: https://en.wikipedia.org/wiki/Focus_(geometry)
    locator: lead section
same_as:
  wikidata: Q3568
  wikipedia: Focus (geometry)
---

## Summary

A focus of a conic is a special point that is used to define the conic. An ellipse and a hyperbola have two foci, a parabola has one, and the focus of a circle is its centre.