Classification :
Carbohydrates may be classified into two broad groups.
1. Sugars and
2. Non-sugars or polysaccharides.

Sugars : Sugars are sweet crystalline substances and soluble in water.

Monosaccharides : The monosaccharides are polyhydroxy aldehydes or polyhydroxy ketones which cannot be hydrolysed into simpler sugars.
They may again be classified according to the nature of carbonyl group.
(a) Aldoses, which contain an aldehyde group
(b) Ketoses, which contain a keto group
The aldoses and ketoses are further divided into sub-groups on the basis of the number of carbon atoms in their molecules, as trioses, tetroses, pentoses, hexoses etc.
Thus monosaccharides are generally referred to as aldotrioses, aldotetroses, aldopentoses, aldohexoses, ketohexoses etc.
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