Carbohydrates

n. class of organic compounds of carbon hydrogen and oxygen

Carbohydrates (from 'hydrates of carbon') or saccharides (Greek σάκχαρον meaning "sugar") are simple organic compounds that are aldehydes or ketones with many hydroxyl groups added, usually one on each carbon atom that is not part of the aldehyde or ketone functional group. Carbohydrates are the most abundant of the four major classes of biomolecules, which also include proteins, lipids and nucleic acids. They fill numerous roles in living things, such as the storage and transport of energy (starch, glycogen) and structural components (cellulose in plants, chitin in animals). Additionally, carbohydrates and their derivatives play major roles in the working process of the immune system, fertilization, pathogenesis, blood clotting, and development.
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Noun
1. an essential structural component of living cells and source of energy for animals; includes simple sugars with small molecules as well as macromolecular substances; are classified according to the number of monosaccharide groups they contain
(synonym) saccharide, sugar
(hypernym) macromolecule, supermolecule
(hyponym) ribose

Components of food containing carbon, hydrogen and oxygen. The term carbohydrate encompasses simple sugars, monosaccharides (eg. Glucose) and disaccharides (eg. Sucrose), oligosaccharides (containing several monosaccharide units) and polysaccharides. Starch is the only important food polysaccharide that can be digested in the small intestine. Starch and simple sugars are "available carbohydrates". The indigestible polysaccharides are the main components of "dietary fibre". 

an organic compound made of carbon, hydrogen, and oxygen; carbohydrates are monosaccharides, disaccharides, oligosaccharides, or polysaccharides depending on degree of polymerization of sugars.