# MI5

> English word · Proper noun · frequency rank #33,328

## Definitions
1. The domestic intelligence and counter-espionage agency of the United Kingdom, which operates in secret and whose primary function is to spy on terrorist organizations and others viewed as a threat to British national security. Formally known as the Security Service.

## Etymology
Abbreviation of Military Intelligence, Section Five.

## Easily confused with
- **my** (https://plainspell.com/en/vs/mi5-vs-my)
- **Mr** (https://plainspell.com/en/vs/mi5-vs-mr)
- **MS** (https://plainspell.com/en/vs/mi5-vs-ms)
- **MM** (https://plainspell.com/en/vs/mi5-vs-mm)
- **MO** (https://plainspell.com/en/vs/mi5-vs-mo)
- **MP** (https://plainspell.com/en/vs/mi5-vs-mp)
- **MT** (https://plainspell.com/en/vs/mi5-vs-mt)
- **ML** (https://plainspell.com/en/vs/mi5-vs-ml)
- **MN** (https://plainspell.com/en/vs/mi5-vs-mn)
- **mu** (https://plainspell.com/en/vs/mi5-vs-mu)
- **MK** (https://plainspell.com/en/vs/mi5-vs-mk)
- **MW** (https://plainspell.com/en/vs/mi5-vs-mw)
- **MV** (https://plainspell.com/en/vs/mi5-vs-mv)
- **MJ** (https://plainspell.com/en/vs/mi5-vs-mj)
- **Mx** (https://plainspell.com/en/vs/mi5-vs-mx)
- **mom** (https://plainspell.com/en/vs/mi5-vs-mom)
- **Mrs** (https://plainspell.com/en/vs/mi5-vs-mrs)
- **mix** (https://plainspell.com/en/vs/mi5-vs-mix)
- **min** (https://plainspell.com/en/vs/mi5-vs-min)
- **mum** (https://plainspell.com/en/vs/mi5-vs-mum)

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/mi5