Litmus

//ˈlɪtməs// noun

noun ·Uncommon ·Advanced level

Definitions

Noun
  1. 1
    A dyestuff extracted from certain lichens, that changes color when exposed to pH levels greater than or less than certain critical levels. uncountable
  2. 2
    a coloring material (obtained from lichens) that turns red in acid solutions and blue in alkaline solutions; used as a very rough acid-base indicator wordnet
  3. 3
    A simple test of acidity in a liquid using litmus, usually in the form of litmus paper. countable, uncountable
  4. 4
    A simple test of any attribute; a litmus test. countable, uncountable

Synonyms

All synonyms
indicatorlacmuslacmuslitmus test

Example

More examples

"When investigating the pH (acidic, neutral, alkaline) of a liquid, don't soak the litmus paper completely in the liquid but just put the end of the paper in it."

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.

Related phrases

litmus milklitmus paperlitmus testlecanora tartarealitmus paperlitmus test

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.