What is a Homologous Series ? ... A Homologous Series is a group of organic chemical compounds, usually listed in order of increasing size, that have a similar structure (and hence also similar properties) and whose structures differ only by the number of CH2 units in the main carbon chain. Learn about the homologous series in organic chemistry with simple explanations, clear examples, key characteristics, and importance in understanding compounds for NEET, JEE, and board exams. Learn homologous series in organic chemistry with definition, examples, general formulas, importance, differences from functional groups, and FAQs.