chlorine

American  

[klawr-een, -in, klohr-] / ˈklɔr in, -ɪn, ˈkloʊr- /

noun

• chlorines
  plural

1. a halogen element, a heavy, greenish-yellow, incombustible, water-soluble, poisonous gas that is highly irritating to the respiratory organs, obtained chiefly by electrolysis of sodium chloride brine: used for water purification, in the making of bleaching powder, and in the manufacture both of chemicals that do not contain chlorine, as ethylene glycol, and of those that do. Cl; 35.453; 17.

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chlorine British  

/ ˈklɔːriːn, ˈklɔːrɪn /

noun

1. a toxic pungent greenish-yellow gas of the halogen group; the 15th most abundant element in the earth's crust, occurring only in the combined state, mainly in common salt: used in the manufacture of many organic chemicals, in water purification, and as a disinfectant and bleaching agent. Symbol: Cl; atomic no: 17; atomic wt: 35.4527; valency: 1, 3, 5, or 7; density: 3.214 kg/m³; relative density: 1.56; melting pt: –101.03°C; boiling pt: –33.9°C

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chlorine Scientific  

/ klôr′ēn′ /

1. A greenish-yellow, gaseous element of the halogen group that can combine with most other elements and is found chiefly in combination with the alkali metals as chlorates and chlorides. Chlorine is highly irritating and poisonous. It is used in purifying water, as a disinfectant and bleach, and in the manufacture of numerous chemical compounds. Atomic number 17; atomic weight 35.453; freezing point −100.98°C; boiling point −34.6°C; specific gravity 1.56 (−33.6°C); valence 1, 3, 5, 7.

2. See Periodic Table See Note at chlorophyll

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chlorine Cultural  

1. A chemical element, normally a corrosive gas, that is widely used for sterilization and cleaning.

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Discover More

Chlorine in CFCs is believed to be responsible for the ozone hole.

Chlorine is added to drinking water to kill bacteria.

Other Word Forms

Derived Forms

• chlorinous
  adjective

Inflected Forms

Nouns

• chlorines
  plural

Etymology

Origin of chlorine

First recorded in 1800–10; chlor- ¹ + -ine ²

Compare meaning

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

• chlorine vs. chloride
• chloramine vs. chlorine

Explanation

Chlorine is a chemical that's commonly used to purify water. That bleach-like smell at the public swimming pool? That's chlorine. At room temperature, chlorine is a greenish-yellow gas. It was identified as a separate element in 1810 by the British chemist Sir Humphry Davy, who named it after the Greek khlōros, "pale green." Modern uses of chlorine have ranged from a weapon in chemical warfare to public sanitation. Today, most public water is treated with chlorine to kill dangerous bacteria.

Example Sentences

See Examples For:

chlorine chlorines

As I push through the doors, the smell of chlorine hits me.

From BBC ● Aug. 31, 2026

PVC is especially challenging to recycle because it contains chlorine and can include a wide range of additives depending on how it was manufactured.

From Science Daily ● Aug. 29, 2026

Workers will then disinfect the repaired section with chlorine, test the water quality, then dechlorinate the water and discharge it into a storm drain.

From Los Angeles Times ● Jul. 20, 2026

The National Park Service said it is using pumps to treat the water with what it called nanobubble ozone technology to kill the algae, along with hydrogen peroxide, which it said is milder than chlorine.

From Barron's ● Jun. 16, 2026

Everything is set up, though, the rented thick-stemmed wineglasses, the bottles of mediocre hooch, the mineral water for teetotalers, because who would serve unadulterated chlorine from the tap?

From "Cat's Eye" by Margaret Atwood

To produce dicarbon, they started with molecules consisting of two carbon atoms and four chlorine atoms and used a laser to strip off the chlorines, leaving only dicarbon.

From New York Times ● Jan. 7, 2022

The trans isomer, formed when the chlorines are positioned at a 180° angle, has very different properties from the cis isomers.

From Textbooks ● Feb. 14, 2019

Related Words

• bleach
• disinfectant