phenol, any of a family of organic compounds characterized by a hydroxyl (―OH) group attached to a carbon atom that is part of an aromatic ring. Besides serving as the generic name for the entire family, the term phenol is also the specific name for its simplest member, monohydroxybenzene (C 6 H 5 OH), also known as benzenol, or carbolic acid.. Phenols are similar to alcohols but form ...