litmus

American  

[lit-muhs] / ˈlɪt məs /

noun

1. a blue coloring matter obtained from certain lichens, especially Roccella tinctoria. In alkaline solution litmus turns blue, in acid solution, red: widely used as a chemical indicator.

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litmus British  

/ ˈlɪtməs /

noun

1. a soluble powder obtained from certain lichens. It turns red under acid conditions and blue under basic conditions and is used as an indicator

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litmus Scientific  

/ lĭt′məs /

1. A colored powder, obtained from certain lichens, that changes to red in an acid solution and to blue in an alkaline solution. Litmus is a mixture of various closely related heterocyclic organic compounds.

2. ◆ Litmus is typically added to paper to make litmus paper, which can be used to determine whether a solution is basic or acidic by dipping a strip of the paper into the solution and seeing how the paper changes color.

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litmus Cultural  

1. In chemistry, a kind of paper used to tell whether a solution is an acid or a base. Acids turn blue litmus paper red; bases turn red litmus paper blue. Other testing paper or sophisticated instruments can be used to measure the pH of a solution more precisely.

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Discover More

The term litmus is often used to refer to a general and simple test: “Your vote on this issue is a litmus test of your political philosophy.”

Etymology

Origin of litmus

1495–1505; earlier lytmos < Old Norse litmosi dye-moss, equivalent to lit- color, dye + mosi moss

Example Sentences

Sunday’s showdown with Kansas, and coach Bill Self, will be the ultimate litmus test of Pitino’s bold strategy.

From The Wall Street Journal • Mar. 21, 2026

They also provide a valuable litmus test for contemporary romance.

From Salon • Mar. 19, 2026

Still, many wondered if the Lakers’ litmus test would come from facing the defending champion Oklahoma City Thunder on Monday night.

From Los Angeles Times • Feb. 10, 2026

The watch became a litmus test of sorts: A guy was classified as a potential keeper if he didn’t mind the watch.

From Slate • Jan. 25, 2026

Her effect upon blue litmus paper would assuredly have been most striking and instantaneous.

From A Woman's Burden by Hume, Fergus