What does hydroxyl mean?
A hydroxyl is the chemical group formed when an oxygen atom and a hydrogen atom are joined together, conventionally written –OH. It is a common functional group in chemistry, appearing in alcohols, sugars, and many other organic compounds. The name combines elements of “hydrogen” and “oxygen,” reflecting the group’s composition. In a molecule, a hydroxyl group can influence solubility, acidity, and the ability to form hydrogen bonds with surrounding molecules. The term is also used in related technical contexts, especially when discussing the hydroxyl radical, a highly reactive form of the group. For general scientific writing, hydroxyl is most often encountered in the phrase “hydroxyl group,” while chemists may use the shorter form “–OH” in structural formulas and diagrams.
A chemical group consisting of an oxygen atom bonded to a hydrogen atom, written –OH.
"This compound has a hydroxyl group that can participate in hydrogen bonding."
The term is commonly used attributively, as in “hydroxyl group.”
Having or containing one or more hydroxyl groups.
"The researchers studied the surface properties of hydroxyl-modified materials."
This attributive use is common in chemical and biological writing.
The plural is used when referring to multiple hydroxyl groups or multiple hydroxyl species.
"The polymer chains contain several hydroxyls along their backbone."
A hydroxyl group is the –OH team that makes many molecules able to interact with water.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does hydroxyl come from?
The word was formed in the 19th century from elements of “hydrogen” and “oxygen,” with the suffix -yl used to indicate a group or radical. Its name reflects the chemical composition of the –OH group. The terminology belongs to the developing vocabulary of organic and inorganic chemistry, in which related names such as hydroxide, hydrate, and hydrogen were also established.
Related word forms
How hydroxyl is actually used
In chemistry, hydroxyl is usually used as an attributive modifier: hydroxyl group. The term hydroxyl radical specifically refers to a free radical, not merely any –OH group.