The hydroxide ion, represented as OH⁻, is a negatively charged ion composed of one oxygen atom and one hydrogen atom. It plays a crucial role in chemistry, particularly in acid-base reactions. Hydroxide ions are commonly found in basic (alkaline) solutions, where they can neutralize acids. In water, OH⁻ ions can form when water molecules dissociate, contributing to the pH level of a solution. A higher concentration of hydroxide ions indicates a more basic solution, while a lower concentration suggests acidity. Understanding OH⁻ is essential in various fields, including biochemistry and environmental science.