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

Allowing your body to rest gives it time to flush out the lactic acid that can build up after intense physical activity. —Sherri Gordon, Health, 6 May 2026

So do moisturizers containing lactic acid and anti-aging products with alpha-hydroxy acids. —Ryan Brennan may 1, Sacbee.com, 1 May 2026

Compounds like lactic acid, ammonia and uric acid (found in sweat) are major attractants, according to USA Today. —Ryan Brennan may 1, Fort Worth Star-Telegram, 1 May 2026

Sweat, breath and body heat Mosquitoes are drawn to compounds in sweat including lactic acid, ammonia and uric acid, USA Today reported. —Ryan Brennan, Miami Herald, 1 May 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