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halogen

American  
[hal-uh-juhn, -jen, hey-luh-] / ˈhæl ə dʒən, -ˌdʒɛn, ˈheɪ lə- /

noun

Chemistry.
halogens plural
  1. any of the electronegative elements, fluorine, chlorine, iodine, bromine, and astatine, that form binary salts by direct union with metals.


halogen British  
/ ˈhæləˌdʒɛn, həˈlɒdʒɪnəs /

noun

  1. any of the chemical elements fluorine, chlorine, bromine, iodine, and astatine. They are all monovalent and readily form negative ions

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

halogen Scientific  
/ hălə-jən /
  1. Any of a group of five nonmetallic elements with similar properties. The halogens are fluorine, chlorine, bromine, iodine, and astatine. Because they are missing an electron from their outermost shell, they react readily with most metals to form salts.

  2. See Periodic Table


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Derived Forms

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Nouns

Etymology

Origin of halogen

First recorded in 1835–45; halo- + -gen

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Explanation

A halogen is a chemical element that forms a salt when it reacts with metal. Halogen lamps are illuminated by bulbs that contain a halogen and an inert gas. There are five halogens in the periodic table of chemical elements: fluorine, chlorine, bromine, iodine, and astatine. The halogens are all highly reactive, which means they're quick to form bonds with other elements. What they often end up becoming is some kind of salt, including common table salt. In fact, the literal translation of halogen is "salt-producer," from Greek roots hals, "salt," and gen, "giving birth to."

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Vocabulary lists containing halogen

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

He did a more-than-competent job—he was Rossini after all—but the result always reminds me of shining a halogen light into a place of hallowed dim.

From The Wall Street Journal May 15, 2026

Also, LED lights "are a lot more directional, so you've got this much brighter, whiter light in a very directional point hitting your eye compared to the more diffuse halogen ones".

From BBC Feb. 18, 2026

The housing for halogen bulbs is not compatible with LED bulbs, and a retrofitted car will not pass its annual MOT check-up.

From BBC Oct. 27, 2025

Overall, the present results underscore the importance of halogen bonds in the photoinduced dynamics, offering a better understanding of the synergistic spin transition.

From Science Daily Jun. 4, 2024

As the broiling sun set, a different kind of American landscape lit up: The halogen floodlights from the truck stop could be seen for miles.

From "Geeks: How Two Lost Boys Rode the Internet Out of Idaho" by Jon Katz

By combining different halide salts, researchers created MXenes with two or even three types of surface halogens in carefully controlled proportions.

From Science Daily Apr. 4, 2026

Firstly, they are two to three times as bright as traditional halogens, and their "colour temperature" is bluer and whiter, which mimics natural daylight.

From BBC Feb. 18, 2026

A team from France and Germany has now studied the rapid decay of molecules containing halogens.

From Science Daily Dec. 2, 2024

The binary compounds of a metal with the halogens are the halides.

From Textbooks Feb. 14, 2019

It burns with dazzling brilliancy in oxygen, and combines directly with many other elements, especially with sulphur and the halogens.

From An Elementary Study of Chemistry by McPherson, William

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