If there is an organic chemical called "X-ic acid", which has an acidic -OH group, "X-yl" often means the radical formed by removing that -OH group: see acyl.
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).