A homologous series is a series of carbon compounds that have same chemical properties but different physical properties and the differences between two successive compounds is \(-CH_2\).

For example: Alkanes family. The general formula of Alkane is \(C_nH_{2n+2}\).

Methane \(CH_4\)
Ethane \(CH_3CH_3\)
Propane \(CH_3CH_2CH_3\)
Butane \(CH_3CH_2CH_2CH_3\)