The structural isomers are isomers that vary in the atomic arrangement of molecules without any relation to the spatial arrangement.
There are various types of structural isomers like chain isomerism, functional group isomerism, and position isomerism.
Chain isomerism is referred to two or more compounds that are having a similar molecular formula but different arrangements of carbon atoms in straight or branched chains.
Positional isomers are the isomers that are having the same carbon skeleton and the same functional groups but differ from each other in the position of the functional groups on or in the carbon chain.
Functional isomers are the isomers when substances have the same molecular formula but different functional groups.
That is, position isomerism is a part of structural isomerism.
Hence, position isomerism is a part of structural isomerism.