Linear and branched alkanes

Alkanes, whose carbons are connected in a continuos chain (no branched) are called straight-chain alkanes.

The family of straight-chain alkanes is an example of  a homologous series. A homologous series of compounds is one in which succesive members differ by one methylene (CH2) group.  The general formula for alkanes homologs is CH3(CH2)nCH3.  Propane (CH3CH2CH3, with n=1) and butane (CH3CH2CH2CH3, with n=2) are homologs.

Alkanes, whose carbon chains branch, are called branched-chain alkanes.