Carbohydrates are used by plants to store the energy of sunlight using photosynthesis. The term is most common in biochemistry, where it is a synonym of saccharide, a group that includes sugars, starch, and cellulose.  Carbohydrates contain oxygen atoms, while hydrocarbons do not. Their generic chemical formula is Cm(H2O)n.
Carbohydrates are one of the main components of food. The combustion of carbohydrates is one of the main sources of energy for cells. The synthesis of carbohydrates is not a process of the chemical industry at this time. Biological systems are required to produce carbohydrates in significant amounts.
As an energy source, carbohydrates store about 4000 kilocalories per kg, or 17 MJ/kg.