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

This process allows researchers to control which halogen atoms, including chlorine, bromine, or iodine, attach to the surface.

From Science Daily • Apr. 4, 2026

For iodine, the recommended dietary reference intake for females aged 19 and older is 150 mcg/day, increasing to 220 mcg/day during pregnancy and 290 mcg/day during lactation.

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

Famine and food shortages in Gaza mean pregnant women are not getting enough folate, iron, vitamin B12 and iodine.

From Salon • Oct. 31, 2024

When I got home, Mama was on the phone and I went into the bathroom and got the iodine.

From "Bad Boy" by Walter Dean Myers