: 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
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These bacteria immediately start feeding on lactose, the natural sugar in milk, and produce lactic acid as a byproduct.
—
Samantha Agate, Charlotte Observer, 21 May 2026
Though cow's milk is high in protein and other nutrients like calcium and vitamin D, consider opting for a high-protein plant milk to get nearly the same amount of protein without the lactose.
—Cristina Mutchler, Verywell Health, 19 May 2026
Lactic acid bacteria in kefir grains produce β-galactosidase, which helps break down lactose into lactic acid, making kefir slightly tangy.
—Merve Ceylan, Health, 15 May 2026
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
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Samantha Agate, Charlotte Observer, 21 May 2026
Though cow's milk is high in protein and other nutrients like calcium and vitamin D, consider opting for a high-protein plant milk to get nearly the same amount of protein without the lactose.
—Cristina Mutchler, Verywell Health, 19 May 2026
Lactic acid bacteria in kefir grains produce β-galactosidase, which helps break down lactose into lactic acid, making kefir slightly tangy.
—Merve Ceylan, Health, 15 May 2026
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
See All Example Sentences for lactose
Cite this Entry
“Lactose.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/lactose. Accessed 24 May. 2026.
Copy CitationKids 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
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