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

For Infants and Children Most infants can digest lactose. —Amber J. Tresca, Verywell Health, 14 Mar. 2025

While some people with lactose intolerance may be able to consume small amounts of lactose without triggering symptoms, people who are very sensitive to lactose may experience gas, bloating, and diarrhea after consuming yogurt and cottage cheese. —Jillian Kubala, Health, 4 Mar. 2025

The infection damages the gut lining, leading to a lack of lactase, the enzyme that breaks down lactose. —Adrianna Rodriguez, USA TODAY, 7 Jan. 2025

Dairy Products Birds don’t have the enzyme necessary to break down lactose that is in milk and other dairy products. —Kait Hanson, Southern Living, 26 Dec. 2024

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