Monosaccharides, or simple sugars, are the simplest carbohydrates and serve as the building blocks for complex carbohydrates. They are classified by the number of carbon atoms in the molecule using a prefix for the carbon count and the suffix -ose, such as three-carbon trioses (e.g., glyceraldehyde), five-carbon pentoses (e.g., ribose), and six-carbon hexoses (e.g., glucose).