-one \-one\ [From Gr. -w`nh, signifying, female descendant.] (Chem.) A suffix indicating that the substance, in the name of which it appears, is a ketone; as, acetone. -one \-one\(Chem.) A termination indicating that the hydrocarbon to the name of which it is affixed belongs to the fourth series of hydrocarbons, or the third series of unsaturated hydrocarbonsl as, nonone.