An active, colorless, odorless, gaseous element (O; at. no. 8; at. wt. 15.9994), essential to all vegetable and animal life, constituting about one fifth of the total volume of the atmosphere, and occurring as a constituent of water and of most animal and vegetable products, acids, bases, and salts.

【化】氧(元素符号 O；原子序 8；原子量 15.9994)。