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 lactic acid thickens the mixture and gives the cheese its signature subtle tang. —Daryl Austin, USA Today, 5 Sep. 2025

Sourdough Sourdough bread, known for its unique and tangy flavor, is made by fermenting lactic acid bacteria and yeast. —Lindsey Desoto, Verywell Health, 2 Sep. 2025

Compared to a slow suffocation on the deck of a boat, Ikejime can dramatically improve the quality of the fish by reducing stress for the animal and minimizing the release of stress hormones like cortisol, adrenaline, and lactic acid. —Akiko Katayama, Forbes.com, 31 Aug. 2025

In addition to containing gentle AHAs mandelic and lactic acids, the formula features pore-clarifying salicylic acid as well as mangosteen peel extract. —Emily Orofino, Vogue, 25 Aug. 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