Monomers are similar identical units covalently bonded to each other to from polymers. The monomer of carbohydrates are monosaccharides. Carbohydrates are polymers so its monomer is a simple sugar called monosaccharide.
Carbo-hydr-ate shows that the compound contains Carbon, Hydrogen and oxygen (Ate is 3 oxygen's yet in glucose is 6). Monomers of carbohydrates such as glucose contain all three elements therefore can be classed as carbohydrates.