lactose

noun lac·tose \ ˈlak-ˌtōs , -ˌtōz \

|Updated on: 16 Jun 2018

Definition of lactose

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

See lactose defined for English-language learners

See lactose defined for kids

Recent Examples of lactose from the Web

Gone are the days of gritting your teeth through gritty soy lattes to avoid the gastrointestinal effects of lactose and dairy fat; a new, smoother, tastier league of mylks has arrived to appease dairy haters of every ilk.

— marian bull, GQ, "The Best Non-Dairy Milks for Every Occasion," 12 June 2018
Or the large percentage of individuals who have trouble digesting lactose, the sugar in milk, and prefer something other than dairy milks that may be more easily digested.

— lisa drayer, CNN, "Got alt-milk? How plant-based alternatives compare," 31 May 2018
Made simply from walnuts, water, and a pinch of salt and sugar, the creamy, dairy-free milk provides a change of pace from almond, soy, or other ordinary lactose-free milks.

— grace dickinson, Philly.com, "Beyond bugs: 12 unique (and strange) ingredients at Mom's Organic Market and what to do with them," 16 May 2018
Those who can't tolerate lactose or don't want to consume animal products can easily do without dairy.

— Allure, "Do Gluten-Free, Sugar-Free, or Low-Carb Diets Actually Work?," 16 May 2018
Other recent research, backed in part by the New Zealand government, concluded that a small group of lactose-intolerant women didn’t feel nauseated after drinking A2 milk.

— mike cherney, WSJ, "Controversial New Milk Shakes Up Big Dairy," 24 Apr. 2018
Who, outside of vegans and the lactose intolerant, doesn’t love those biscuits?

— jenee osterheldt, chicagotribune.com, "Red Lobster’s waffle and lobster combo: The taste of disappointment," 24 Apr. 2018
Around two-thirds of people world-wide have trouble digesting lactose, a naturally occurring sugar in milk.

— bee wilson, WSJ, "Soy, Almond, Pea or Oat? The Reinvention of Milk," 11 May 2018
The bakery franchise claims to be founded upon a commitment that all ingredients must be animal-free and free of dairy, lactose, eggs and cholesterol.

— linda gandee/special to cleveland.com, cleveland.com, "Cinnaholic cinnamon buns coming to Westlake," 7 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'lactose.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of lactose

International Scientific Vocabulary

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First Known Use: 1857

in the meaning defined above

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LACTOSE Defined for English Language Learners

lactose

noun

Definition of lactose for English Language Learners

chemistry : a type of sugar that is present in milk

LACTOSE Defined for Kids

lactose

noun lac·tose \ ˈlak-ˌtōs \

Definition of lactose for Students

: a sugar that is found in milk

Medical Dictionary

lactose

noun lac·tose \ ˈlak-ˌtōs, -ˌtōz \

medical Definition of lactose

: 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