Isomer
different compounds with the same molecular formula
Stereoisomers
isomers that differ only in the arrangement of atoms in space
structural (constitutional) isomers
isomers that differ in the order in which atoms are bonded together
configurational isomers
stereoisomers that can only be interconverted through bond breakage (isolable at room temperature)
diastereomers
configurational isomers that are not mirror images of one another
geometric(al) isomers
diastereomers that differ in their cis-trans arrangement on a ring or double bond
enantiomers
mirror-image, non-superimposable stereoisomers
conformational isomers
stereoisomers related by rotations about a single bond (generally noticeable at room temperature)
conformational enantiomers
enantiomers related by rotation about bonds (see above forms of n-butane)