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

Talk to a dermatologist to determine if lactic acid is right for your skin type and your skincare needs. —Sherri Gordon, Health, 14 Oct. 2025

The alpha hydroxy acids are courtesy of both lactic acid (arguably the gentlest AHA out there) and fruit extracts, while white willow bark serves as a natural source of BHA. —Deanna Pai, Vogue, 14 Oct. 2025

Think NormaTec compression boots for lactic acid legs, Hypervolt percussion massagers, and back wraps that soothe muscle tension after a day on the piste. —Adam H. Graham, AFAR Media, 14 Oct. 2025

However, after microbiologists successfully made yogurt in a lab in the early 1900s, there was a shift from traditional yogurt to a simplified, industrialized version, which only contains two species of lactic acid bacteria, the researchers said. —Amarachi Orie, CNN Money, 3 Oct. 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