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

It’s made with olive squalane to hydrate, prebiotics to balance the microbiome and lactic acid to brighten. —Celia Shatzman, Forbes.com, 29 June 2025

Kefir grains composition: Kefir grains are gel-like substances made from lactic acid bacteria, yeast, acetic acid bacteria, and polysaccharides (a type of carbohydrate). —Melissa Nieves, Verywell Health, 11 June 2025

Fruit is the overwhelmingly predominant flavor, but the lactic acid produced by the brew’s yeast is bright and punchy. —Camila Pedrosa, Sacbee.com, 18 Apr. 2025

Buttermilk or Yogurt Buttermilk and yogurt contain lactic acid, which can help exfoliate and lighten pigmentation. —Heather Jones, Verywell Health, 16 June 2025

Word History

First Known Use

1790, in the meaning defined above

Rhymes for lactic acid

• antacid
• placid

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

ˈdē- 

: 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

ˈel- 

: the levorotatory form obtained by biological fermentation of sucrose

c

or DL-lactic acid

ˈdē-ˈel- 

: 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