chlorine

noun

chlo·​rine ˈklȯr-ˌēn 

-ən

: a halogen element that is isolated as a heavy greenish-yellow diatomic gas of pungent odor and is used especially as a bleach, oxidizing agent, and disinfectant in water purification see Chemical Elements Table

Examples of chlorine in a Sentence

Recent Examples on the Web

Both chlorine bleach and oxygen bleach will oxidize iron, causing yellow or red discoloration. —Brandee Gruener, Southern Living, 31 Jan. 2026

Making sure your pool has the right balance of chemicals, including chlorine and muriatic acid, will help ensure that even if below-freezing temperatures last longer than expected, your pool won’t freeze. —Michael Butler, Miami Herald, 30 Jan. 2026

The facility had no chlorine test strips. —Veronica Fernandez-Alvarado january 30, Sacbee.com, 30 Jan. 2026

The report references the case of a detainee at an ICE facility who drank tap water that was contaminated with high levels of chlorine. —Lautaro Grinspan, AJC.com, 27 Jan. 2026

Word History

First Known Use

1810, in the meaning defined above

Phrases Containing chlorine

• chlorine dioxide
• chlorine monoxide

Rhymes for chlorine

• organochlorine

Kids Definition

chlorine

noun

chlo·​rine ˈklō(ə)r-ˌēn 

ˈklȯ(ə)r-, 

-ən

: a nonmetallic element that is found alone as a heavy greenish yellow irritating gas having two atoms per molecule and a strong odor and that is used especially as a bleach, oxidizing agent, and disinfectant in water purification see element

Medical Definition

chlorine

noun

chlo·​rine ˈklō(ə)r-ˌēn, ˈklȯ(ə)r-, -ən 

: a halogen element that is isolated as a heavy greenish yellow gas of pungent odor and is used especially as a bleach, oxidizing agent, and disinfectant in water purification

—symbol Cl see Chemical Elements Table