What are Monosaccharides?

Monosaccharides are simple sugars with a formula Cn (H2O)n.
They are the simplest group of carbohydrates that can not be hydrolyzed more.
The definition is "Sugars that on hydrolysis yield no further lower sugars."
Based on the functional group they are classified into the following
Aldoses: here the functional group is aldehyde examples are glyceraldehyde and glucose.
Ketoses: here the functional group is keto examples are dihydroxyacetone and fructose.
Based on the number of carbon atoms they are divided into
Trioses with 3 C
Tetroses with 4 C
Pentose with 5 C
Hexose with 6 C
Heptose with 7 C