Ketoses are one of the subgroups of monosaccharides (mono=1, saccharide=sugar, single sugars) in which carbon number 2 of the sugar molecule has a keto group attached to it. Simple enough, right ! Therefore, any sugar with a keto group attached to the second carbon is called ketosugar. So, to further classify a ketosugar we look at how many carbons the molecule has. For example, a hexose (Greek, hexos=6) is a sugar with six carbons. Therefore, if the sugar has 6 carbons and a keto group attached to the second carbon, then we call the sugar a ketohexose. Of course we cannot see how many carbons are in a molecule, because of their exceedingly small size. However, these classifications are important, as they reinforce the sugars characteristics and also can give us some insight into how they are used in our body, as we shall learn.