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

Choose an exfoliant that has an AHA, such as lactic acid, or other hydrating properties to soothe your skin while exfoliating. —Sherri Gordon, Health, 26 Sep. 2025

In addition to this, the lactic acid bacteria produced in the fermentation process may also help the body flush out sodium. —New Atlas, 21 Sep. 2025

Inspired by the Japanese treat both in formula and texture, the Iota Supermochi Body Exfoliator+ contains soothing sweet rice water and exfoliating red bean extract—alongside ingredients like lactic acid, sea salt, and urea—to gently resurface your skin from the neck down. —Sophia Panych, Allure, 16 Sep. 2025

The non-greasy formula is enriched with lactic acid, shea butter and sodium hyaluronate, and is the perfect skin-quencher for post-summer revivals. —Angelina Villa-Clarke, Forbes.com, 16 Sep. 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