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

Some researchers have recently developed flame-retardant, hydrophobic, high-strength, breathable cotton fabric by dual covalent crosslinking of amino-containing siloxane segments, phosphorus-containing monomers with several reaction sites, and hydroxyl-rich cellulose segments. —Prabhat Ranjan Mishra, Interesting Engineering, 18 Sep. 2025

During photocatalysis, light is absorbed by photocatalysts that have the ability to create electron-hole pairs, which generate free hydroxyl radicals that are able to react with target pollutants and degrade them. —IEEE Spectrum, 23 Jan. 2023

More proof: Glycerin, one of the best moisturizers available, is a polyol, a type of alcohol with multiple hydroxyl groups. —Elizabeth Siegel, Allure, 26 Sep. 2022

After each lightning flash, the researchers found the concentrations of hydroxyl and hydroperoxyl increased by thousands of parts per trillion, Science News reports. —Elizabeth Gamillo, Smithsonian Magazine, 4 May 2021

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