What is "pentose"

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.

n. (context carbohydrate English) A sugar or saccharide containing five carbon atoms.

n. any monosaccharide sugar containing five atoms of carbon per molecule

A pentose is a monosaccharide with five carbon atoms. Pentoses are organized into two groups. Aldopentoses have an aldehyde functional group at position 1. Ketopentoses have a ketone functional group in position 2 or 3.