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

Barrière’s first-to-market lactose intolerance patch is launching in Walmart and promises the same results as Lactaid products. —Laya Neelakandan, CNBC, 6 May 2026

Simple carbohydrates include single sugars, such as glucose or fructose, and two sugars linked together, such as sucrose – table sugar – or lactose, milk sugar. —Julie Pollock, The Conversation, 1 May 2026

Oat milk is a mildly sweet and creamy drink that is lactose-free and vegan-friendly. —Jillian Kubala, Health, 29 Apr. 2026

Another commenter on r/PeanutButter also pointed out that Nutella Peanut is dairy-free, unlike the original spread, which means lactose will not be an obstacle for foodies who typically avoid Nutella. —Joseph Erbentraut, Better Homes & Gardens, 19 Apr. 2026

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