-yl

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An organic acid radical: carbonyl.

Century Dictionary and Cyclopedia

1. n. In chem., a suffix commonly used with radicals, denoting the fundamental part, the origin: as, methyl, CH₃, is the fundamental radical of wood alcohol, CH₃OH, methylic ether, (CH₃)₂O, methyl anime, CH₃NH₂, etc.

Wiktionary

1. n. organic chemistry A univalent radical or functional group formed from a given molecule. Thus "propyl" from propane, "benzyl" from benzene, and so forth.

GNU Webster's 1913

1. (Chem.) A suffix used as a characteristic termination of chemical radicals; as in ethyl, carbonyl, hydroxyl, etc.