A borate is any of a range of boron oxyanions, anions containing boron and oxygen, such as orthoborate BO3−3, metaborate BO−2, or tetraborate B4O2−7; or any salt of such anions, such as sodium metaborate, Na[BO2] and borax (Na)2[B4O7]. The name also refers to esters of such anions, such as trimethyl borate B(OCH3)3.