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

Explanation

Litmus is a special dye that's used to determine how acidic a substance is. Scientists use litmus to test liquids or gases to see if they're an acid or a base. Litmus is the mix of dyes that's used to make litmus paper, a scientific tool that makes it easy to see if a material has an acidic pH. Made from lichen, litmus can be absorbed onto paper which turns blue to indicate an alkaline substance and red if it's acidic. Litmus comes from the Middle Dutch word lijkmoes, which combines lac, "red resinous substance" and moes, "pulp."

Example Sentences

His most accomplished juveniles to date include Litmus Test, recent winner of the Los Alamitos Futurity; Brant, the Del Mar Futurity winner who was third in the Breeders’ Cup Juvenile, and Desert Gate.

From Los Angeles Times • Dec. 25, 2025

Litmus now owns Perry's stake in the master recordings and publishing for the records, meaning it will collect any future royalties the music earns.

From BBC • Sep. 19, 2023

The five studio albums were released under Perry's contract with Capitol Records, whose former president Dan McCarroll is the co-founder of Litmus Music.

From Reuters • Sep. 18, 2023

Eventually, Page and her team came up with something they called the Litmus Group to oversee the content of the Dome, composed of cultural luminaries such as Alan Yentob and Michael Grade.

From The Guardian • Mar. 12, 2020

Litmus, largely used in chemistry, is derived from it.

From The Sailor's Word-Book An Alphabetical Digest of Nautical Terms, including Some More Especially Military and Scientific, but Useful to Seamen; as well as Archaisms of Early Voyagers, etc. by Belcher, Edward, Sir