Isomers are molecules with the same molecular formula but different chemical structure. Butan-2-ol and diethyl ether are isomers.

There are two principal types of isomers: estructural isomers and stereoisomers.

Structural isomers are compounds that have the same molecular formula but different conectivity, the atoms are arranged in different ways in both compounds.

Butane and 2-methylpropane are chain isomers.

2-Pentanol and 3-pentanol are position isomers.

2-Butanol and diethyl ether are functional group isomers.