Stearic acid (first syllable pronounced either steer or stair) is the saturated fatty acid with an 18 carbon chain and has the IUPAC name octadecanoic acid. It is a waxy solid, and its chemical formula isC₁₈H₃₆O₂, or CH₃(CH₂)₁₆COOH. Its name comes from the Greek word genitive: which means tallow. The salts and esters of stearic acid are called stearates.