Isomer (source code)

= Isomer

<Isomers> have the same molecular formula but different arrangements of their atoms. Constitutional isomers differ in connectivity; stereoisomers retain connectivity but differ in spatial arrangement.

For example, ethanol and dimethyl ether share $\mathrm{C_2H_6O}$ but connect their atoms differently. Two enantiomers instead have mirror-related spatial structures. Formula, connectivity, and stereochemistry therefore encode different levels of chemical identity.