noun, often attributive
pro·​tein | \ ˈprō-ˌtēn How to pronounce protein (audio) also ˈprō-tē-ən How to pronounce protein (audio) \

Definition of protein

1 : any of various naturally occurring extremely complex substances that consist of amino-acid residues joined by peptide bonds, contain the elements carbon, hydrogen, nitrogen, oxygen, usually sulfur, and occasionally other elements (such as phosphorus or iron), and include many essential biological compounds (such as enzymes, hormones, or antibodies)
2 : the total nitrogenous material in plant or animal substances

Examples of protein in a Sentence

You need more protein in your diet. These foods are an excellent source of protein. These foods have all of the essential proteins.
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Recent Examples on the Web These are excellent sources of protein and can be paired with crackers and cheese or placed over salad greens for an easy lunch or dinner. Jean Chen Smith,, "Guide to healthy New Year in 2020: These small changes are better than big resolutions," 31 Dec. 2019 Each episode follows him hunting or fishing for some source of protein, as well as doing some foraging, and then the preparation of the food, either by him or a chef., "BRIDGTON, Maine — Daniel Vitalis, who was once a big influencer in the raw-food vegan movement and is angling to become an even bigger one in the modern hunter-gatherer movement, was crunching through the Maine woods on a recent morning, rifle in hand, looking for a squirrel to kill for lunch.," 26 Dec. 2019 Mercury poisoning is marked by a wide range of neurological symptoms, including tremors, anxiety, numbness, tingling, and unusually high levels of protein in urine. Scottie Andrew, CNN, "A woman was permanently injured from a skin-lightening cream tainted with an extremely toxic form of mercury - the first such case in the US," 26 Dec. 2019 Cells communicate many complex messages through DNA and RNA to make millions of proteins. Scientific American, "The Power of Spheres," 25 Dec. 2019 About 50%of the food the nonprofit organization delivers is fresh fruit and vegetables, dairy and a form of protein. Jessica Seaman, The Denver Post, "Denver’s We Don’t Waste helps get fresh produce and prepared food to those in need," 21 Dec. 2019 Our bodies need nine amino acids—the building blocks of protein—to make muscle. National Geographic, "These traditional diets can lead to long lives," 17 Dec. 2019 The foxes that live in the area see the ravens and also garner their part of the protein. John Schandelmeier, Anchorage Daily News, "When it comes to predator control, balancing biology and the desires of hunters is a tricky task," 14 Dec. 2019 This North-African-inspired supper packs a punch of protein, and makes for great lunch leftovers too! Heat broiler. Woman's Day Kitchen, Woman's Day, "Moroccan Meatballs with Roasted Tomatoes and Chickpeas," 10 Dec. 2019

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

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First Known Use of protein

1886, in the meaning defined at sense 1

History and Etymology for protein

French protéine, from Late Greek prōteios primary, from Greek prōtos first — more at proto-

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Time Traveler for protein

Time Traveler

The first known use of protein was in 1886

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Statistics for protein

Last Updated

9 Jan 2020

Cite this Entry

“Protein.” The Dictionary, Merriam-Webster Inc., Accessed 17 January 2020.

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More Definitions for protein


How to pronounce protein (audio) How to pronounce protein (audio)

English Language Learners Definition of protein

: a substance found in foods (such as meat, milk, eggs, and beans) that is an important part of the human diet


pro·​tein | \ ˈprō-ˌtēn How to pronounce protein (audio) \

Kids Definition of protein

: a nutrient found in food (as meat, milk, eggs, and beans) that is made up of many amino acids joined together, is a necessary part of the diet, and is essential for normal cell structure and function


noun, often attributive
pro·​tein | \ ˈprō-ˌtēn How to pronounce protein (audio) , ˈprōt-ē-ən How to pronounce protein (audio) \

Medical Definition of protein

1 : any of numerous naturally occurring extremely complex substances (as an enzyme or antibody) that consist of amino acid residues joined by peptide bonds, contain the elements carbon, hydrogen, nitrogen, oxygen, usually sulfur, and occasionally other elements (as phosphorus or iron), that are essential constituents of all living cells, that are synthesized from raw materials by plants but assimilated as separate amino acids by animals, that are both acidic and basic and usually colloidal in nature although many have been crystallized, and that are hydrolyzable by acids, alkalies, proteolytic enzymes, and putrefactive bacteria to polypeptides, to simpler peptides, and ultimately to alpha-amino acids
2 : the total nitrogenous material in plant or animal substances especially : crude protein

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More from Merriam-Webster on protein

Rhyming Dictionary: Words that rhyme with protein

Spanish Central: Translation of protein

Nglish: Translation of protein for Spanish Speakers

Britannica English: Translation of protein for Arabic Speakers Encyclopedia article about protein

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a plan in which a last survivor takes all

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