pro·​tein ˈprō-ˌtēn How to pronounce protein (audio)
ˈprō-tē-ən How to pronounce protein (audio)
plural proteins
: 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)
: the total nitrogenous material in plant or animal substances
: a food (such as meat or tofu) that is rich in protein
Having grown up with brisket or roasted chicken as the protein of choice at a Chanukah table, I was intrigued to find that Italian Jews traditionally celebrate the Festival of Lights with a special fried chicken recipe and wanted to give it a try.Sophie Panzer
There are 10 sandwiches to choose from, with different proteins like sausage, salami and mortadella.Cesar Hernandez
With plant proteins such as nuts or soy foods, we get good amounts of fiber and polyunsaturated fats …Walter Willett

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.
Recent Examples on the Web Add protein: Crisp bacon, roasted chicken, leftover turkey, or flaked salmon can be added to turn this side salad into a main course. Marianne Williams, Southern Living, 22 Sep. 2023 On the morning of Towson football’s game at Morgan State on Saturday, Nathan Kent drained a protein shake and took aim at a trash can about 10 feet away inside the team’s locker room. Edward Lee, Baltimore Sun, 20 Sep. 2023 Amino acids are the building blocks of proteins, and proteins are the building blocks of everything else in the body, so even small changes can have large and far-reaching effects. WIRED, 19 Sep. 2023 Getting to that amount may involve adding in protein shakes, protein bars, or other protein supplements, or just eating more protein-rich foods like eggs and meat. Amy Marturana Winderl, SELF, 19 Sep. 2023 Spirulina, a blue algae chock-full of protein, essential amino acids, vitamins, and minerals, with anti-inflammatory, antioxidant, and restorative actions. Alessandra Signorelli, Vogue, 18 Sep. 2023 Some of these proteins break down or transport certain medications through the body. Kayla B. Rowe, Fortune Well, 17 Sep. 2023 Find it in your detergent containers, milk jugs, and protein powder tubs. Ali Francis, Bon Appétit, 15 Sep. 2023 To give these products texture, taste and mouthfeel, Upside has added soy protein, wheat protein, fat, seasonings and more. Tim Carman, Washington Post, 15 Sep. 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'protein.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


borrowed from French protéine, from Late Greek prōteîos "of the first quality" (from Greek prôtos "first, foremost" + -eios, adjective suffix, originally from s-stems) + -ine -ine entry 1 — more at proto-

Note: The term protein was introduced by the Dutch chemist Johannes Gerardus Mulder (1802-80), as French protéine in the article "Sur la composition de quelques substances animales" (Bulletin des sciences physiques et naturelles en Néerlande, vol. 1 [1838], pp. 104-19), and as Dutch protein in the article "Over Proteine en hare Verbindingen en Ontleidingsproducten" (Natuur- en scheikundig Archief, vol. 6 [1838], pp. 87-162). Though Mulder in the beginning of the papers expresses gratitude to Jöns Jakob berzelius for his support, he does not mention any connection between Berzelius and the novel word. In the twentieth century, however, it was discovered that Berzelius had suggested the word to Mulder in a letter written July 10, 1838: "Le nom protéine que je vous propose pour l'oxyde organique de la fibrine et de l'albumine, je voulais le dériver de πρωτειος, parce qu'il paraît être la substance primitive ou principale de la nutrition animale que les plantes préparent pour les herbivores et que ceux-ci fournissent ensuite aux carnassiers." ("The name protein, which I propose for the organic oxide of fibrin and albumin, I wish to derive from prōteios, because it appears to be the primitive or principal substance of animal nutrition, which plants prepare for herbivores, and which the latter then provide for carnivores." — quoted in H.B. Vickery, "The origin of the word protein," Yale Journal of Biology and Medicine, vol. 22, no. 5 [May, 1950], pp. 387-93.) In the French article, Mulder glosses the word prōteîos with Latin primarius "primary": "The organic material, being a general principal of all the constituent parts of the animal body and being found, as we will see later, in the vegetable kingdom, could be named protein from prōteîos …" ("La matière organique, étant un principe général de toutes les parties constituantes du corps animal, et se trouvant, comme nous verrons tantôt, dans le règne végétal, pourrait se nommer Protéine de πρωτεῖος primarius.") This appears to be Mulder's own interpretation of the Greek word, as the leading Greek dictionary of the time, Franz Passow's Handwörterbuch der griechischen Sprache (4. Ausgabe, 1831) defines it only as a masculine noun: "first rank, first place, primacy, priority" ("erster Rang, erster Platz, Vorrang, Vorzug"). For details, see the article by H.B. Vickery cited above and Harold Hartley, "Origin of the Word 'Protein'," Nature, vol. 168, issue 4267 (August 11, 1951), p. 244.

First Known Use

1886, in the meaning defined at sense 1

Time Traveler
The first known use of protein was in 1886

Dictionary Entries Near protein

Cite this Entry

“Protein.” Dictionary, Merriam-Webster, Accessed 27 Sep. 2023.

Kids Definition


: any of numerous substances that consist of chains of amino acids, contain the elements carbon, hydrogen, nitrogen, oxygen, and often sulfur, include many compounds (as enzymes and hormones) essential for life, and are supplied by various foods (as meat, milk, eggs, nuts, and beans)

Medical Definition


: 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
: the total nitrogenous material in plant or animal substances
especially : crude protein

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