A homologous series is a series of organic compounds in which all members have

• The same general formula.
• The same functional group.
• Similar chemical properties.
• Successive members differ by a -CH₂- unit (methylene group) in their molecular formula.
• There is a regular gradation in their physical properties (like boiling point, melting point and density) as the molecular mass increases.

You can find detailed analysis of the topics in the carbon and its compounds class 10 NCERT solutions PDF.