lactic acid

noun

: a hygroscopic organic acid C3H6O3 present normally especially in muscle tissue as a by-product of anaerobic glycolysis, produced in carbohydrate matter usually by bacterial fermentation, and used especially in food and medicine and in industry

Examples of lactic acid in a Sentence

Recent Examples on the Web
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Here’s another natural deo that uses mandelic and lactic acids—this time in a cooling, roll-on formula. Sara Coughlin, SELF, 23 July 2025 The esthetician recommended maintaining a weekly lactic acid exfoliant and a daily vitamin C serum to keep results consistent and help prevent new dark spots from forming. Larry Stansbury, Essence, 22 July 2025 The lactic acid in yogurt is gentler than vinegar or lemon juice, so the chicken will not turn soft or mushy. Beth Dooley, Boston Herald, 9 July 2025 The yeasts also ensure that lactic acid, a small amount of alcohol, and carbon dioxide are present in kefir. Desireé Oostland, Vogue, 22 May 2025 See All Example Sentences for lactic acid

Word History

First Known Use

1790, in the meaning defined above

Time Traveler
The first known use of lactic acid was in 1790

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Cite this Entry

“Lactic acid.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/lactic%20acid. Accessed 29 Jul. 2025.

Kids Definition

lactic acid

noun
lac·​tic acid
ˌlak-tik-
: an organic acid present especially in muscle tissue as a result of the breakdown of carbohydrates (as glycogen), is made from carbohydrates usually by fermentation by bacteria, and is used especially in food and medicine

Medical Definition

lactic acid

noun
: a hygroscopic organic acid C3H6O3 that is known in three optically isomeric forms:
a
or D-lactic acid : the dextrorotatory form present normally in blood and muscle tissue as a product of the anaerobic metabolism of glucose and glycogen
b
or L-lactic acid : the levorotatory form obtained by biological fermentation of sucrose
c
or DL-lactic acid : the racemic form present in food products and made usually by bacterial fermentation (as of whey or raw sugar) but also synthetically, and used chiefly in foods and beverages, in medicine, in tanning and dyeing, and in making esters for use as solvents and plasticizers

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