litmus test

noun

: a test in which a single factor (such as an attitude, event, or fact) is decisive

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Litmus Test Has Scientific Origins

It was in the 14th century that scientists discovered that litmus, a mixture of colored organic compounds obtained from lichen, turns red in acid solutions and blue in alkaline solutions and, thus, can be used as an acid-base indicator. Six centuries later, people began using litmus test figuratively. It can now refer to any single factor that establishes the true character of something or causes something to be assigned to one category or another. Often it refers to something (such as an opinion about a political or moral issue) that can be used to make a judgment about whether someone or something is acceptable or not.

Examples of litmus test in a Sentence

The party is using attitudes about gun control as a litmus test for political candidates.
Recent Examples on the Web
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The Club World Cup will be new Real Madrid coach Xabi Alonso’s first litmus test Ahead of a fresh La Liga campaign and attempt to dethrone FC Barcelona, new Real Madrid coach Xabi Alonso can test the waters at the Club World Cup. Tom Sanderson, Forbes.com, 28 May 2025 Patriotism became a litmus test, and scholars who applied their expertise to offer critical analyses of America’s revered narratives were suspected of harboring a dangerous un-American ideology. Time, 20 May 2025 Related article German spy agency labels far-right AfD ‘extremist’ More than 10 million Romanians cast their vote in Sunday’s election, which was widely seen as a choice between East and West and a litmus test for the rise of Trump-style nationalism in Europe. Mitchell McCluskey, CNN Money, 19 May 2025 The Dodgers and Diamondbacks meeting is not a litmus test. Fabian Ardaya, New York Times, 9 May 2025 See All Example Sentences for litmus test

Word History

First Known Use

1913, in the meaning defined above

Time Traveler
The first known use of litmus test was in 1913

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Cite this Entry

“Litmus test.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/litmus%20test. Accessed 30 Jun. 2025.

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