All the organic compounds made up of carbon, hydrogen and oxygen in which the ratio of carbon, hydrogen and oxygen is 1:2:1 are called carbohydrates or sugars. There are also many compounds that do not have a 1:2:1 ratio, including carbohydrates. According to the modern definition, all aldehyde and ketone compounds containing hydroxyl groups are called carbohydrates. Or, polyhydroxy aldehydes, polyhydroxyketones and their derivatives are collectively called carbohydrates.