litmus

[ lit-muh s ]
/ ˈlɪt məs /

noun

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.

Origin of litmus

1495–1505; earlier lytmos < Old Norse litmosi dye-moss, equivalent to lit- color, dye + mosi moss
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for litmus

British Dictionary definitions for litmus

litmus
/ (ˈlɪtməs) /

noun

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

Word Origin for litmus

C16: perhaps from Scandinavian; compare Old Norse litmosi, from litr dye + mosi moss
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for litmus

litmus
[ lĭtməs ]

n.

A water-soluble blue powder derived from lichens that changes to red with increasing acidity and to blue with increasing basicity.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for litmus

litmus
[ lĭtməs ]

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.♦ 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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Culture definitions for litmus

litmus
[ (lit-muhs) ]

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.

notes for litmus

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.”
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.