Define homologous series of organic compounds. Mention any two characteristics of homologous series.

(N/A) homologous series is a group of organic compounds having the same functional group and similar chemical properties,in which the successive members differ by a $CH_2$ unit.
Characteristics:
$(i)$ All members of a homologous series can be represented by the same general molecular formula.
(ii) Any two adjacent members of the series differ by one carbon atom and two hydrogen atoms,i.e.,a $CH_2$ unit in their molecular formula.