lactic acid


: 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 This formula features a blend of potent chemical exfoliants, including glycolic acid, lactic acid, tartaric acid, citric acid, and salicylic acid, to target excess oil production, dull skin, and hyperpigmentation. Jessie Quinn, Peoplemag, 25 Mar. 2024 Those two new components—lactic acid and diacetyl—make buttermilk an MVP in waffles and pancakes. Karla Walsh, Better Homes & Gardens, 22 Mar. 2024 Youth to the People 10% AHA + Yerba Mate Smoothing Energy Body Scrub, which combines AHAs and olive seed powder, and Sunday Riley Charcoal Smoothie, which uses salicylic acid and lactic acid plus biodegradable wax are two standouts. Hannah Baxter, Allure, 5 Mar. 2024 Yogurt is made by combining heated milk and bacteria, which begins the fermentation process and converts the sugar in milk to lactic acid and allows the milk to thicken and become tart. Clare Mulroy, USA TODAY, 25 Feb. 2024 Other helpful ingredients include willow bark to manage excess oil, lactic acid to exfoliate, along with vitamins A, C, E, Coenzyme Q10, and antioxidants to nourish skin. Chaunie Brusie, Rn, Parents, 26 Feb. 2024 That culture then produces lactic acid, which causes the milk protein to thicken into a creamy, slightly tart mixture. Genevieve Ko, San Diego Union-Tribune, 21 Feb. 2024 This helps balance out the formula’s lactic acid, an exfoliator that can help reduce the appearance of pores and fine lines. Macaela MacKenzie, Glamour, 17 Feb. 2024 Key ingredients: 10% glycolic and lactic acids, pumice buffing beads, vitamin E | Base: Beads | Size: 8 oz. Alyssa Brascia, Peoplemag, 16 Feb. 2024

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'lactic acid.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1790, in the meaning defined above

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

Dictionary Entries Near lactic acid

Cite this Entry

“Lactic acid.” Dictionary, Merriam-Webster, Accessed 16 Apr. 2024.

Kids Definition

lactic acid

lac·​tic acid
: 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

: a hygroscopic organic acid C3H6O3 that is known in three optically isomeric forms:
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
or L-lactic acid : the levorotatory form obtained by biological fermentation of sucrose
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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