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

And to treat oil and shine, this is also enriched with live yeast extracts and lactic acid to regulate sebum production and reduce breakouts over time. —Kiana Murden, Vogue, 12 Dec. 2025

More recently, research has emerged to suggest that the byproducts of fermentation (like lactic acid from lactic acid bacteria) can enhance digestion in their own right. —Caroline Tien, SELF, 10 Dec. 2025

The fermentation process transforms milk's natural sugar (lactose) into lactic acid. —Md Published, Verywell Health, 9 Dec. 2025

During this time, probiotics found in the foods produce lactic acid. —Merve Ceylan, Health, 28 Nov. 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