Question

What is the difference between structural isomers, geometric isomers, and stereo isomers?

Answer 1

Structural isomers differ in constitution, but not molecular formula.

Geometric isomers are a special case of the former, but the substituents of the double bond are "rotated" in different ways ( cis/trans is an easy example)

Stereoisomers have the same constitution, but differ in special arrangement. By extension,

Enantiomers are non-superimposable mirror images, where each chirality center is inverted relative to its enantiomer.

Diastereomers are non-superimposable non-mirror images, where only one chirality center is in common, but one (or all of) the others are inverted.

Meso compounds are molecules with more than one chirality center, but have a reflectional plane of symmetry (and are hence achiral).