ribose

from WordNet (r) 3.0 (2006)

ribose
    n 1: a pentose sugar important as a component of ribonucleic
         acid

from The Collaborative International Dictionary of English v.0.48

Pentose \Pen"tose\, n. [Penta- + -ose.] (Chem.)
   Any of a group of sugars of the formula {C5H10O5}, such as as
   {arabinose} or {ribose}; -- so called from the five carbon
   atoms in the molecule. They are not fermented by yeast.
   [Webster 1913 Suppl.]