pentanone and pentanone are:

2-pentanone and 3-pentanone have the same molecular formula (C5H10O) and the same carbon skeleton (pentane chain). They differ only in the position of the carbonyl group (at C2 vs C3), making them positional isomers. They are not chain isomers (skeleton same), not tautomers (no proton shift), and not metamers (though alkyl groups differ, the primary classification is based on functional group position).