noun, often attributive
io·​dine | \ ˈī-ə-ˌdīn How to pronounce iodine (audio) , -dᵊn, -ˌdēn \

Definition of iodine

1 : a nonmetallic halogen element that is an essential nutrient in the human diet and is used especially in medicine, photography, and analytical chemistry — see Chemical Elements Table
2 : a tincture of iodine used especially as a topical antiseptic

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Did You Know?

Iodine is a nonmetallic chemical element and the heaviest nonradioactive halogen. It is a very nearly black crystalline solid that can turn to a deep violet, irritating vapor. In nature it is never found uncombined, and occurs mostly in brines and seaweeds. Dietary iodine is essential for thyroid gland function, so table salt usually has potassium iodide added to prevent iodine deficiency. Elemental iodine is used in medicine, in synthesizing some organic chemicals, in manufacturing dyes, in analytical chemistry, and in photography. The radioactive isotope I-131, with an eight-day half-life, is very useful in medicine and other applications.

Examples of iodine in a Sentence

Recent Examples on the Web At the park, there’s a pop-up tent where crews tend to medical equipment including IV drip bags, bandages, gauze and saucers filled with iodine. oregonlive, "Australia, on fire, tries to save koalas, mitigate ‘animal apocalypse’," 16 Jan. 2020 The essay itself is a mind-numbing look at what Infowars employees do and how the site makes money—wait for the part about the iodine pills and the Geiger counters. Ellen Mcgirt, Fortune, "The Nazi Salute in a West Virginia Correctional Training Class," 6 Dec. 2019 Russian residents are rushing to buy iodine tablets after reports of radiation were posted online following a deadly blast at a military test site. Zach Wade, CNN, "Quickly catch up on the day's news," 12 Aug. 2019 Public health officials have long combatted this problem by adding essential nutrients, such as iodine, iron, and folate, to common food staples. Robert F. Service, Science | AAAS, "New polymer-coated vitamins and minerals could fight malnutrition in low-income countries," 13 Nov. 2019 More specifically, the Undaria Algae Oil—Michele’s body oil of choice—is made with Undaria Pinnatifida extract, a brown marine algae that boasts iodine, iron, potassium, calcium, B vitamins, and fucoidan (a hydrating compound). Christie Calucchia,, "This Is the Anti-Aging Body Oil Lea Michele Uses to Hydrate and Firm Her Skin," 26 Sep. 2019 Soon after, Tarek was scheduled for surgeries and radioactive iodine therapy to beat both forms of cancer. Taylor Mead, House Beautiful, "Flip or Flop Star Tarek El Moussa Is Officially Cancer Free Six Years After His Diagnosis," 18 Mar. 2019 The Takeaway: Time to stock up on iodine tablets, perhaps. Graeme Mcmillan, WIRED, "While You Were Offline: The New 'New Colossus'," 18 Aug. 2019 Civilians of two northern Russian cities flocked to pharmacies Friday to purchase large quantities of iodine after a mysterious explosion at a nearby military testing site Thursday. Fox News, "Russian pharmacies report rise in sales of iodine near site of mysterious military explosion," 10 Aug. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'iodine.' 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 iodine

1814, in the meaning defined at sense 1

History and Etymology for iodine

French iode "iodine" (borrowed from Greek ioeidḗs "violet-colored," from íon "the color violet"—going back to *wion, akin to the source of Latin viola "the violet flower"— + -o-eidēs -oid entry 2) + -ine entry 2 (after chlorine, fluorine) — more at violet

Note: The French word iode was apparently introduced by the chemists Bernard Courtois (1777-1838) and Joseph Louis Gay-Lussac (1778-1850); cf. B. Courtois, "Découverte d'une substance nouvelle dans le Vareck," Annales de chimie, tome 88 (1813), p. 305: "La substance nouvelle, que depuis on a nommé iode à cause de la belle couleur violette de sa vapeur, a bien tout l'aspect d'un métal." ("The new substance, which since has been named iode because of the beautiful violet color of its vapor, has all the appearance of a metal.") Note that a borrowing from Greek ioeidḗs should properly have yielded ioïde in French rather than iode; the direct source of the latter may have been iṓdēs "rust-colored," a derivative of íos "rust, verdigris," taken erroneously to be a derivative of íon "the color violet."

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Time Traveler for iodine

Time Traveler

The first known use of iodine was in 1814

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Statistics for iodine

Last Updated

21 Jan 2020

Cite this Entry

“Iodine.” The Dictionary, Merriam-Webster Inc., Accessed 21 January 2020.

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More Definitions for iodine


How to pronounce iodine (audio)

English Language Learners Definition of iodine

: a chemical element that is used especially in medicine and photography


io·​dine | \ ˈī-ə-ˌdīn How to pronounce iodine (audio) , -dᵊn \

Kids Definition of iodine

1 : a chemical element found in seawater and seaweeds and used especially in medicine and photography
2 : a solution of iodine in alcohol used to kill germs


noun, often attributive
io·​dine | \ ˈī-ə-ˌdīn How to pronounce iodine (audio) , -əd-ᵊn How to pronounce iodine (audio) , -ə-ˌdēn How to pronounce iodine (audio) \

Medical Definition of iodine

1 : a nonmetallic halogen element obtained usually as heavy shining blackish gray crystals and used especially in medicine (as in antisepsis and in the treatment of goiter and cretinism) and in photography and chemical analysis symbol I — see Chemical Elements Table
2 : a tincture of iodine used especially as a topical antiseptic

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More from Merriam-Webster on iodine

Rhyming Dictionary: Words that rhyme with iodine

Spanish Central: Translation of iodine

Nglish: Translation of iodine for Spanish Speakers

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

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