A functional group is a group of atoms responsible for the characteristic reactions of a particular compound.
Nomenclatures is the systematic method of naming organic compounds
In chemistry, a homologous series is a series of compounds with the same general formula, usually varying by a single parameter—such as the length of a carbon chain.
 Functional groups - When an atom or group of atoms bonded to a carbon atom in the chain or ring of an organic compound, shown some characteristic properties of their own, they are termed as a functional group. Homologous series - A homologous series is a family of organic compounds containing a particular characteristic group and exhibiting similar properties. For example, the compounds given below belong to the alcohol family.