Isomers (compounds with the same molecular formula, but different arrangement of atoms and properties)

Structural Isomers (same molecular formula, but different structural formula and arrangement of atoms)

Functional Isomers

Positional Isomers

Chain Isomers

Stereoisomers (same molecular and structural formula, but different spatial arrangement of atoms and bonds)

Geometrical/Cis-trans Isomers (isomers differ in their spatial arrangement about a Carbon double bond)

Cis Isomers

Trans Isomers

Optical Isomers (isomers differ in the arrangement of atoms in a 3 dimensional space, creating mirror images of each other)

Enantiomers