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

Not to mention, the lactose in dairy is a FODMAP, which could worsen endo belly in some folks. —Erica Sloan, SELF, 25 Apr. 2025

While the levels are much lower than in milk, people with severe lactose intolerance or dairy allergies may still react to it. —Allison Herries, Verywell Health, 2 Apr. 2025

Simple carbs are natural, digestible sugars such as ones found in foods like milk (lactose), table sugar (sucrose) and fruit (fructose). —Daryl Austin, USA Today, 29 Mar. 2025

Low in lactose, gluten free and made with all natural ingredients, LS Cream exudes style and luxury while staying true to its Caribbean heritage. —Essence, 27 Mar. 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