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 from the yogurt tenderizes the meat while the fatty mayo insulates it, making for a particularly juicy result. —Editors Of Bon Appétit, Bon Appetit Magazine, 11 June 2026

Some butter is cultured by adding lactic acid bacteria. —Rosemary Trout, The Conversation, 10 June 2026

The main ingredients include gentle exfoliating acids like lactic acid and salicylic acid, plus hydrating panthenol and soothing allantoin to minimize irritation and redness. —Alanna Martine Kilkeary, Glamour, 8 June 2026

The sourdough microbes, particularly the lactic acid bacteria (LAB), give several benefits to our body's gastrointestinal system, according to a June 2021 study published in the medical journal Microorganisms. —Melissa Kravitz Hoeffner, Martha Stewart, 6 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