Cetyl \Ce"tyl\, n. [Gr. ? whale + -yl.] (Chem.) A radical, {C16H33}, not yet isolated, but supposed to exist in a series of compounds homologous with the ethyl compounds, and derived from spermaceti. Hexdecyl \Hex"de*cyl\, n. [Hex- + decyl.] (Chem.) The essential radical, {C16H33}, of hecdecane.