---
tag: VG1FBHH7XW
kind: concept
name: Sqb2
sources:
  - wikipedia: en:73634@r1376316324
    locator: Glossary of mathematical symbols, section Brackets > Square brackets
    note: adopted
    mention: wikipedia://en/73634#67UE
    sections: [Summary]
inventory: [EAHR8WG6CM]
---

## Summary

Closed interval: if $a$ and $b$ are [[real numbers|08J2M1JYAG]] such that $a\le b$, then $[a,b]$ denotes the closed interval defined by them.

Commutator (group theory): if $a$ and $b$ belong to a group, then $[a,b]=a^{-1}b^{-1}ab$.

Commutator (ring theory): if $a$ and $b$ belong to a [[ring|0B1261B5ED]], then $[a,b]=ab-ba$.

Denotes the Lie bracket, the operation of a Lie algebra.