lac·​tose | \ ˈlak-ˌtōs How to pronounce lactose (audio) , -ˌtōz \

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

Examples of lactose in a Sentence

Recent Examples on the Web By piecing together Neolithic pottery fragments and ancient human genomes, scientists may have solved the riddle of how European lactose tolerance evolved. Brian Handwerk, Smithsonian Magazine, 27 July 2022 For cats who can tolerate lactose, milk should still be seen as a treat in moderation but not make up the whole diet, says. Mythili Devarakonda, USA TODAY, 25 July 2022 Rather, the pallets are stocked with cartons of lactose-free milk. Bayliss Wagner, USA TODAY, 24 June 2022 European Union food standards ban corn syrup, commonly found in U.S. formula, and require at least 30% of the carbohydrates to come from lactose, which scientists believe is preferable. Emily Ekins, WSJ, 22 May 2022 Some formulas utilize glucose and corn syrup for their carbohydrates as opposed to lactose which is the main carbohydrate source in breast milk. Stefani Sassos, Ms, Rdn, Cso, Cdn, Nasm-cpt, Good Housekeeping, 24 May 2022 Without that enzyme, lactose cannot be absorbed (malabsorption). Dr. Keith Roach, oregonlive, 19 May 2022 Cow's milk protein allergies are not to be confused with an intolerance for lactose, which is an inability to catalyze a specific dairy sugar. Christiaan Hetzner, Fortune, 17 May 2022 WildCare rehabilitators in Bloomington warn that no wild animal should be given cow’s milk as the lactose can be fatal to most infant animals. Karl Schneider, The Indianapolis Star, 21 Mar. 2022 See More

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.

First Known Use of lactose

1847, in the meaning defined above

History and Etymology for lactose

International Scientific Vocabulary

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Time Traveler for lactose

Time Traveler

The first known use of lactose was in 1847

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Dictionary Entries Near lactose



lactose intolerant

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Statistics for lactose

Last Updated

11 Aug 2022

Cite this Entry

“Lactose.” Dictionary, Merriam-Webster, Accessed 14 Aug. 2022.

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More Definitions for lactose


lac·​tose | \ ˈlak-ˌtōs How to pronounce lactose (audio) \

Kids Definition of lactose

: a sugar that is found in milk


lac·​tose | \ ˈlak-ˌtōs, -ˌtōz How to pronounce lactose (audio) \

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

More from Merriam-Webster on lactose Encyclopedia article about lactose


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