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

Here’s another natural deo that uses mandelic and lactic acids—this time in a cooling, roll-on formula. —Sara Coughlin, SELF, 23 July 2025

The esthetician recommended maintaining a weekly lactic acid exfoliant and a daily vitamin C serum to keep results consistent and help prevent new dark spots from forming. —Larry Stansbury, Essence, 22 July 2025

The lactic acid in yogurt is gentler than vinegar or lemon juice, so the chicken will not turn soft or mushy. —Beth Dooley, Boston Herald, 9 July 2025

The yeasts also ensure that lactic acid, a small amount of alcohol, and carbon dioxide are present in kefir. —Desireé Oostland, Vogue, 22 May 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