Hydroxide - Hydroxide is a diatomic anion with chemical formula OH-1. It consists of a hydrogen and an oxygen atom held together by a covalent bond, and carries a negative electric charge.
Hydroxyl radical- {hydro- + oxy(gen) + -yl +radical} - The hydroxyl radical, •OH, is the neutral form of the hydroxide ion (OH-1). It is the monovalent group -OH which contains hydrogen and oxygen. The suffix -yl indicates it's a radical just like carbonyl.