13.1.1—Terms: hydrocarbon as a compound made up of C

A hydrocarbon is a compound made only from carbon and hydrogen atoms. Alkanes, alkenes and alkynes are hydrocarbons; adding oxygen, nitrogen or a halogen makes a different class of organic compound.

The definition is about composition, not whether the molecule is saturated or unsaturated. Use the molecular formula and displayed structure to check the atom types.

C₃H₈ and C₃H₆ are both hydrocarbons, while C₃H₇OH is not because it contains oxygen. The first two can belong to different homologous series.

“Organic” is broader than “hydrocarbon”. Many organic compounds contain heteroatoms and are still organic.