Source : Webster's Revised Unabridged Dictionary (1913)

Pentyl \Pen"tyl\, n. [Penta + -yl.] (Chem.)
   The hypothetical radical, {C5H11}, of pentane and certain of
   its derivatives. Same as {Amyl}.

Amyl \Am"yl\, n. [L. amylum starch + -yl. Cf. {Amidin}.] (Chem.)
   A hydrocarbon radical, {C5H11}, of the paraffine series found
   in amyl alcohol or fusel oil, etc.