What is the difference between hydroxyl, hydroxide and hydroxy?
Hydroxide - Hydroxide is a diatomic anion with chemical formula $\ce{OH-}$. 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.

Hydroxy or hydroxy group: A hydroxy or hydroxy group is the entity with the formula $\ce{-OH}$. It contains oxygen bonded to hydrogen. Hydroxy is also prefix which means containing hydroxyl group.