litmus test
noun
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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
David Frum, The Atlantic, 18 Feb. 2026
All of that offers another pre-playoff litmus test for the Knicks (35-20), who are currently third in the East and seek to build on last year’s trip to the Eastern Conference Finals.
—Peter Sblendorio, New York Daily News, 16 Feb. 2026
Still, many wondered if the Lakers’ litmus test would come from facing the defending champion Oklahoma City Thunder on Monday night.
—Broderick Turner, Los Angeles Times, 10 Feb. 2026
That litmus test can get tricky when evaluating some expenses, such as hotel stays or dinners.
—Nick Sullivan, Charlotte Observer, 10 Feb. 2026
See All Example Sentences for litmus test
Cite this Entry
“Litmus test.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/litmus%20test. Accessed 22 Feb. 2026.
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