lit·​mus | \ ˈlit-məs How to pronounce litmus (audio) \

Definition of litmus

1 : a coloring matter from lichens that turns red in acid solutions and blue in alkaline solutions and is used as an acid-base indicator
2 : the critical factor in a litmus test also : litmus test

Examples of litmus in a Sentence

Recent Examples on the Web In 1988, the litmus tests included abstinence and prayer in school. M.l. Elrick, Detroit Free Press, 24 Apr. 2022 As for those of you who look no further than candidate mailers, NextDoor rants or red vs. blue litmus tests: Sit this one out. Sharon Grigsby, Dallas News, 20 Apr. 2021 Gone are the days of 90-plus votes in favor of a nominee, replaced by partisan votes and clear political litmus tests. Jeff Zeleny, Kevin Liptak And Phil Mattingly, CNN, 4 Feb. 2022 Farmer: This is a litmus-test game for the Chargers. Los Angeles Times, 2 Nov. 2021 His candidacy wasn't about passing litmus tests, but about changing the broad direction of the party. Noah Millman, The Week, 19 Nov. 2021 Ideological litmus tests make no sense when the future of the nation is on the line. Walter Shapiro, The New Republic, 23 Dec. 2021 Moderate Democrats point to her policy stances, which have often stopped short of embracing left-wing litmus tests on issues like single-payer health care and a Green New Deal to combat climate change. New York Times, 1 Dec. 2021 For the moment, Zverev, 24, has yet to reach the top spot and yet to win one of the four major titles that remain tennis’ litmus tests of greatness. Christopher Clarey, New York Times, 21 Nov. 2021 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'litmus.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of litmus

14th century, in the meaning defined at sense 1

History and Etymology for litmus

Middle English litmose, of Scandinavian origin; akin to Old Norse litmosi herbs used in dyeing, from litr color (akin to Old English wlite brightness, appearance) + mosi moss; akin to Old English mōs moss

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Time Traveler for litmus

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The first known use of litmus was in the 14th century

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litmus milk

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Last Updated

4 May 2022

Cite this Entry

“Litmus.” Dictionary, Merriam-Webster, Accessed 19 May. 2022.

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More Definitions for litmus


lit·​mus | \ ˈlit-məs How to pronounce litmus (audio) \

Medical Definition of litmus

: a coloring matter from lichens that turns red in acid solutions and blue in alkaline solutions and is used as an acid-base indicator

More from Merriam-Webster on litmus

Thesaurus: All synonyms and antonyms for litmus

Nglish: Translation of litmus for Spanish Speakers Encyclopedia article about litmus


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