iodine

American  

[ahy-uh-dahyn, -din, ahy-uh-deen] / ˈaɪ əˌdaɪn, -dɪn, ˈaɪ əˌdin /

Sometimes iodin

noun

Chemistry.

1. a nonmetallic halogen element occurring at ordinary temperatures as a grayish-black crystalline solid that sublimes to a dense violet vapor when heated: used in medicine as an antiseptic. I; 126.904; 53; (solid) 4.93 at 20°C.

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iodine British  

/ ˈaɪəˌdiːn /

noun

1. a bluish-black element of the halogen group that sublimates into a violet irritating gas. Its compounds are used in medicine and photography and in dyes. The radioisotope iodine-131 ( radioiodine ), with a half-life of 8 days, is used in the diagnosis and treatment of thyroid disease. Symbol: I; atomic no: 53; atomic wt: 126.90447; valency: 1, 3, 5, or 7; relative density: 4.93; melting pt: 113.5°C; boiling pt: 184.35°C

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iodine Scientific  

/ ī′ə-dīn′ /

1. A shiny, grayish-black element of the halogen group. It is corrosive and poisonous and occurs in very small amounts in nature except for seaweed, in which it is abundant. Iodine compounds are used in medicine, antiseptics, and dyes. Atomic number 53; atomic weight 126.9045; melting point 113.5°C; boiling point 184.35°C; specific gravity (solid, at 20°C) 4.93; valence 1, 3, 5, 7.

2. See Periodic Table

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Etymology

Origin of iodine

First recorded in 1814; from French iode + -ine ² ( def. 2 ); introduced by H. Davy. Ultimately from Greek īṓdēs, originally “rust-colored”, but by folk etymology taken as í(on) “violet” + -ōdēs noun suffix; -ode ¹ ( def. )

Compare meaning

How does iodine compare to similar and commonly confused words? Explore the most common comparisons:

• iodide vs. iodine
• Betadine vs. iodine
• povidone-iodine vs. iodine

Example Sentences

A short walk along an irrigation canal leads to a weathered observation deck rising two stories above a patchwork of saturated flats where saltgrass, iodine bush and cattail take root.

From Los Angeles Times • Apr. 7, 2026

The study published in The American Journal of Clinical Nutrition checked the amounts of choline and iodine in nonprescription and prescription prenatal vitamins.

From Science Daily • Nov. 21, 2024

Included in the lists of items to be kept at home are long-life foods such as tins of beans, energy bars and pasta, and medicines including iodine tablets in case of a nuclear accident.

From BBC • Nov. 17, 2024

Due to the high iodine content in many seaweed species, seaweed consumption could exacerbate thyroid conditions or interfere with thyroid medications.

From Salon • Aug. 5, 2024

I add what I remember to be the right number of drops of iodine for purifying it.

From "The Hunger Games" by Suzanne Collins