Parent monosaccharides are polyhydroxy aldehydes H[CH(OH)]nC(=O)H or polyhydroxy ketones H-[CHOH]n-C(=O)[CHOH]m-H with three or more carbon atoms. The generic term 'monosaccharide' (as opposed to oligosaccharide or polysaccharide) denotes a single unit, without glycosidic connection to other such units. It includes aldoses, dialdoses, aldoketoses, ketoses and diketoses, as well as deoxy sugars, provided that the parent compound has a (potential) carbonyl group.