What term describes a substance primarily made up of carbon and hydrogen?

The term that describes a substance primarily made up of carbon and hydrogen is "hydrocarbon." Hydrocarbons are organic compounds consisting solely of carbon atoms bonded to hydrogen atoms. They are fundamental to many areas of chemistry, particularly in the study of fuels, oils, and various industrial applications.

In contrast, alcohols, ethers, and aldehydes contain additional functional groups that incorporate elements other than carbon and hydrogen. For instance, alcohols contain a hydroxyl (-OH) group, ethers have an oxygen atom connected to two carbon groups, and aldehydes feature a carbonyl group (C=O) with a hydrogen atom attached. These characteristics make hydrocarbons distinct in their structure and properties, essential for identifying and categorizing organic compounds.