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

Dairy products are allowed, but some carnivore dieters avoid them because lactose is a sugar. Abby Langer, SELF, "I'm a Registered Dietitian and I Really Don't Want You to Eat a Carnivore Diet," 7 Aug. 2018 The second is disaccharides, which are just two of these single sugar molecules linked together: sucrose, or table sugar (glucose + fructose); lactose, or milk sugar (glucose + galactose); and maltose, or malt sugar (glucose + glucose). Carolyn L. Todd, SELF, "Can Our Bodies Even Tell the Difference Between Naturally Occurring and Added Sugars?," 24 June 2019 Most of their food is naturally dairy- and lactose-free. Maggie Menderski, The Courier-Journal, "Gluten or dairy-free? Try these 7 allergy-friendly places in Louisville," 24 June 2019 So many factors to consider: cost, setting, inside, outside, lactose-free, vegan, organic, Brent says. Kathy Berdan, Twin Cities, "The Summer of Ice Cream and Parks: A Roseville dad and daughter take a sweet tour through the Twin Cities," 16 June 2019 The cinnamon rolls are free of dairy, lactose, eggs or cholesterol. Linda Zavoral, The Mercury News, "Cinnaholic cinnamon rolls coming to Concord," 5 June 2019 That Got Away is a Milkshake IPA brewed with pineapple, coconut and lactose at 8.4% alcohol and 20 IBUs. Saturday, June 15: Granite City Food & Brewery will offer $5 growler fills of any growler on Father’s Day weekend. Marc Bona,, "Beer calendar: Platform’s 5th anniversary party, Great Lakes dinner and release, more," 3 June 2019 In general, fresher cheeses contain more lactose than aged cheeses, which means cheeses like feta and ricotta, my old favorites, are higher in lactose, and now my enemy. Christian Allaire, Vogue, "I Gave Up Dairy—And My Adult Acne Vanished in Under a Month," 28 July 2018 IPAs brewed with lactose for extra body have also started to multiply (after Tired Hands became the first local to make it). Craig Laban,, "2018 Brewvitational standouts: Peter, haze and pucker," 10 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.

See More

First Known Use of lactose

1847, in the meaning defined above

History and Etymology for lactose

International Scientific Vocabulary

Keep scrolling for more

Learn More about lactose

Statistics for lactose

Last Updated

14 Jul 2019

Look-up Popularity

Time Traveler for lactose

The first known use of lactose was in 1847

See more words from the same year

Keep scrolling for more

More Definitions for lactose



English Language Learners Definition of lactose

chemistry : a type of sugar that is present in milk


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

Rhyming Dictionary: Words that rhyme with lactose Encyclopedia article about lactose

Comments on lactose

What made you want to look up lactose? Please tell us where you read or heard it (including the quote, if possible).


a small bunch of flowers

Get Word of the Day daily email!

Test Your Vocabulary

Farm Idioms Quiz

  • cow coming home
  • What does 'poke' refer to in the expression 'pig in a poke'?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!