# litmus

> English word · Noun · IPA /ˈlɪtməs/ · frequency rank #38,478

## Definitions
1. A dyestuff extracted from certain lichens, that changes color when exposed to pH levels greater than or less than certain critical levels.
2. A simple test of acidity in a liquid using litmus, usually in the form of litmus paper.
3. A simple test of any attribute; a litmus test.

## Etymology
From Middle English litmose, lytmose, litemose, from Old Norse litmosi (“moss used for dyeing”), from lita (“to dye, stain”) + mosi (“moss”), the former from litr (“colour, dye, blee”), from Proto-Germanic *wlitiz, *wlituz (“appearance, blee”), from Proto-Indo-European *wel- (“to see”). Cognate with Old English wlite (“appearance, form, brightness, countenance”). More at moss.

## Easily confused with
- **lotus** (https://plainspell.com/en/vs/litmus-vs-lotus)
- **limbs** (https://plainspell.com/en/vs/limbs-vs-litmus)
- **Linus** (https://plainspell.com/en/vs/linus-vs-litmus)
- **limes** (https://plainspell.com/en/vs/limes-vs-litmus)

## Common misspellings (9)
`iltmus`, `limtus`, `litmmus`, `litmsu`, `litmuss`, `littmus`, `litums`, `llitmus`, `ltimus`

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