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

Chemical exfoliation involves using medications such as alpha hydroxy acids (such as glycolic and lactic acid) to dissolve dead skin cells.3 Exfoliate your skin about once or twice a week for optimal results. —Carrie Madormo, Rn, Mph, Verywell Health, 30 Apr. 2025

During fermentation, while yeast converts sugars into alcohol, lactic acid bacteria, especially Lactobacillus, and other wild microbes can also be active. —Joseph V Micallef, Forbes.com, 26 Apr. 2025

Types Cat probiotics typically contain lactic acid bacteria, including strains such as lactobacillus spp, enterococcus, streptococcus and bifidobacterium. —Bestreviews, Chicago Tribune, 4 Apr. 2025

This natural mask is powered by salicylic acid precursor willow bark extract, which works with AHAs glycolic and lactic acids to gently slough away dead skin and decongest pores to give skin a glow. —Emily Orofino, Vogue, 2 Apr. 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