lactose

noun

lac·​tose ˈlak-ˌtōs 

-ˌtōz

: a disaccharide sugar C₁₂H₂₂O₁₁ that is present in milk and yields glucose and galactose upon hydrolysis and yields especially lactic acid upon fermentation

Examples of lactose in a Sentence

Recent Examples on the Web

The bacteria act on the lactose in milk, changing it to lactic acid. —Amber J. Tresca, Verywell Health, 6 May 2025

Intolerances — like lactose intolerance — are usually digestive issues and generally less severe. —Jenny Lehmann, Discover Magazine, 15 Apr. 2025

Some providers may also recommend eliminating gluten and lactose to reduce the body's inflammatory response, which can adversely affect thyroid function. —Danielle Weiss, Verywell Health, 22 May 2025

When a pope is elected, there will be white smoke, which is created from a combination of potassium chlorate, lactose, and pine resin, which burns clean and pale. —Sarah Turner, Forbes.com, 6 May 2025

Word History

Etymology

International Scientific Vocabulary

First Known Use

1847, in the meaning defined above

Phrases Containing lactose

• lactose intolerant

Rhymes for lactose

• galactose

Kids Definition

lactose

noun

lac·​tose ˈlak-ˌtōs 

: a sugar present in milk that breaks down to give glucose and galactose and on fermentation gives especially lactic acid

called also milk sugar

Medical Definition

lactose

noun

lac·​tose ˈlak-ˌtōs, -ˌtōz 

: a disaccharide sugar C₁₂H₂₂O₁₁ that is present in milk, yields glucose and galactose upon hydrolysis, yields especially lactic acid upon fermentation, and is used chiefly in foods, medicines, and culture media (as for the manufacture of penicillin)

called also milk sugar