Question

what is isomerism?mention the types of isomerism

Answer 1

Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. That excludes any different arrangements which are simply due to the molecule rotating as a whole, or rotating about particular bonds. 

The types are:
1. Structural Isomerism
2. Stereo Isomerism.  

Answer 2

Isomers are compounds that have the same molecular formula but different structures. There are two broad types of isomers: constitutional and stereoisomers. ... Enantiomers and diastereomers are two sub-types of stereoisomers. Enantiomers are isomers that are non-superimposable, mirror images.