hydroxyl

noun

hy·​drox·​yl hī-ˈdräk-səl 

1

: the chemical group, ion, or radical OH that consists of one atom of hydrogen and one of oxygen and is neutral or negatively charged

2

: hydroxide sense 1

hydroxylic

ˌhī-ˌdräk-ˈsi-lik 

adjective

Examples of hydroxyl in a Sentence

Recent Examples on the Web

Whitening strips blend both the natural process of oil pulling with hydrogen peroxide to safely and effectively release oxygen and hydroxyl free radicals for a brighter, whiter smile in as soon as 14 days. —Tory Johnson, ABC News, 12 Mar. 2026

At a molecular level, the simulations showed that UV light causes water molecules to break apart, forming hydronium ions, hydroxyl radicals, and free electrons. —Mrigakshi Dixit, Interesting Engineering, 21 Nov. 2025

This turns the water into hydrogen radicals, hydroxyl radicals, hydrated electrons, molecular hydrogen, and hydrogen peroxide, among others. —New Atlas, 14 Nov. 2025

From this distance, Swift detected the faint ultraviolet glow of hydroxyl (OH), the product of water molecules broken apart by sunlight, the study reports. —Sharmila Kuthunur, Space.com, 10 Oct. 2025

Word History

Etymology

hydr- + ox- + -yl

First Known Use

1869, in the meaning defined at sense 1

Rhymes for hydroxyl

• glyoxal
• methoxyl
• coxal
• voxel
• pyridoxal

Kids Definition

hydroxyl

noun

hy·​drox·​yl hī-ˈdräk-səl 

: a chemical group or ion that consists of one atom of hydrogen and one of oxygen

Medical Definition

hydroxyl

noun

hy·​drox·​yl hī-ˈdräk-səl 

1

: the chemical group or ion OH that consists of one atom of hydrogen and one of oxygen and is neutral or positively charged

2

: hydroxide sense 1

hydroxylic

ˌhī-ˌdräk-ˈsil-ik 

adjective