Define homologous series of carbon compounds. Mention two characteristics of homologous series. Give the name and formula of the next higher homologous of $HCOOH$

A homologous series is a series of hydrocarbons that have similar chemical properties and share the same general formula. They are organic compounds having similar structures and functional groups. The constituents of the homologous series show a gradation in physical properties.
(i) They contain the same functional group throughout the series. Like a homologous series of alcohols will contain only $OH$groups.

(ii) All the members of a homologous series can be represented by the same general formula, like the homologous series of alkanes, which can be represented by the same formula $C_n+2C_n{H}_{(2n+2)}$where $n$ is an integer starting from 1 .
$HCOOH$ is methanoic acid as it has one carbon atom, and the carboxylic acid functional group is present over here $\left(COOH\right).$So its next homologous series would be ethanoic acid $C{H}_{3}COOH$