-yl·i·dene \ˈiləˌdēn, _ə̇l-\noun suffix (-s) Etymology: International Scientific Vocabulary -yl + -idene : bivalent radical derived especially from a saturated hydrocarbon by removal of two hydrogen atoms from the same carbon atom or by removal of the oxygen atom of an aldehyde < citrylidene > — in the system adopted by the International Union of Pure and Applied Chemistry — compare -idene