Why homologous series of carbon compounds are so called?

A homologous series is a group of organic chemical compounds, usually listed in order of increasing size, that have a similar structure and general formula (and hence also similar properties) and whose structures differ only by the number of −CH₂ units in the main carbon chain. CH₃CH₂OH and CH₃CH₂CH₂OH are two consecutive members of alcohol homologous series. Physical properties:- Hydrocarbon chain i.e. CH₃ in CH₃CH₂OH and CH₃CH₂ in CH₃CH₂CH₂OH Chemical properties:- Functional group i.e. −OH