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

The build-up of lactic acid also can trigger muscle repair mechanisms leading to the growth of the muscles as well. — Bruce Y. Lee, Forbes.com, 12 July 2026

Most of the sourdough breads on store shelves, however, include various other ingredients, most commonly yeast to speed up the rise and vinegar or lactic acid to boost sour flavor and also to stabilize the dough and lengthen its shelf life. — Jolene Thym, Mercury News, 6 July 2026

Such cell-sloughing is inherent to all alpha hydroxy acids—yet lactic acid is, in many ways, in a league of its own (hence its presence in all AmLactin products). — Sophie Wirt, InStyle, 3 July 2026

The same active ingredients found in face peels, including glycolic and lactic acid, also appear in body formulas at gentler concentrations suited for larger surface areas. — Lauren Jarvis-Gibson, Charlotte Observer, 30 June 2026

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