Hydroxide ion is a term used in chemistry to describe a molecule with a negative charge in the form of OH−. This ion is formed by the dissociation of water molecules, and it plays a crucial role in many chemical reactions. Synonyms for hydroxide ion include the hydroxyl anion, hydroxide radical, and oxyhydroxide ion. The hydroxyl anion is derived from the dissociation of water molecules and is composed of one oxygen atom and one hydrogen atom. The hydroxide radical is a highly reactive species that can be generated by various means, such as radiation or chemical reactions. Oxyhydroxide ion is a compound that contains both oxygen and hydroxide ions and is often found in geological and environmental systems.