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

These include wild yeast (almost always Saccharomyces cerevisiae), lactic acid and acetic acid bacteria. —Michael Allen, JSTOR Daily, 20 Mar. 2025

Case in point: The Lip Grip Peptide Priming Treatment from Sarah Creal is packed with line-smoothing peptides, alongside exfoliating and hydrating lactic acid. —Siena Gagliano, Allure, 18 Mar. 2025

Most of the polymers incorporated a fair amount of lactic acid, which can also form ester bonds. —John Timmer, Ars Technica, 17 Mar. 2025

In addition to gentle lactic acid, these pads resurface skin with papaya enzyme, which gently removes dead cells without stripping the moisture barrier. —Emily Orofino, Vogue, 12 Mar. 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