Source : Webster's Revised Unabridged Dictionary (1913)

Pentose \Pen"tose\, n. [Penta- + -ose.] (Chem.)
   Any of a group of sugars of the formula {C5H10O5}, as
   arabinose; -- so called from the five carbon atoms in the
   molecule. They are not fermented by yeast.

Source : WordNet®

pentose
     n : any monosaccharide sugar containing five atoms of carbon per
         molecule