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

Combined with AHAs like lactic acid, this product eases the look of fine lines and brightens skin quickly but gently, within weeks of use. —R29 Team, refinery29.com, 29 Jan. 2025

Peter: Those byproducts are: lactate, which is a molecule related to lactic acid. —Outside Online, 16 Jan. 2025

Gentle enough for sensitive skin, the PCA Skin Pigment Gel Pro avoids harsh exfoliants and instead relies on soothing ingredients like lactic acid. —Christa Joanna Lee, Allure, 20 Dec. 2024

Actives like salicylic acid and lactic acid can gently lift away dead skin cells without traumatizing an already sensitive region. —Jenna Ryu, SELF, 20 Dec. 2024

Word History

First Known Use

1790, in the meaning defined above

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