Hydrocarbon: A hydrocarbon is a type of organic molecule made up entirely of hydrogen and carbon atoms. Examples include methane (CH4) and ethane (C2H6).
Functional Group: A functional group is a specific arrangement of atoms within an organic molecule that gives it unique chemical properties. Examples include the hydroxyl group (-OH) found in alcohols and the carboxyl group (-COOH) found in carboxylic acids.
Isomer: Isomers are different compounds that have the same molecular formula but different structural arrangements. They can have distinct physical and chemical properties.