Enol
Enols (also known as alkenols) are alkenes with a hydroxyl group affixed to one of the carbon atoms composing the double bond. Alkenes with a hydroxyl group on both sides of the double bond are called enediols. Deprotonated anions of enols are called enolates. A reductone is a compound that has an enediol structure with an adjacent carbonyl-group.
The C=C double bond with adjacent alcohol gives enols and enediols their chemical characteristics, by which they present keto-enol tautomerism. In keto-enol tautomerism, enols interconvert with ketones or aldehydes.
The words enol and alkenol are portmanteaus of the words "alkene" (or just -ene, the suffix given to C=C double bonded alkenes) and "alcohol" (which represents the enol's hydroxyl group).
Read more about Enol: Keto-enol Tautomerism, Enolates, Enediols, Reductones