The suffix -yl is used in organic chemistry to form names of radicals, either separate or as chemically bonded parts of molecules. It was extracted from the word methyl, whose etymology is described in Methanol#History.

Sometimes words ending in -yl are used with other meanings as a result of ellipsis, for example "vinyl" properly means the monomer radical -CH=CH₂, but "vinyl" is often used as short for the polymer poly(vinyl chloride). Chemical nomenclature