Are all reactions in chemistry are redox reaction? Give your answer with an example.

Although redox reactions are common in chemistry, not all chemical reactions are redox reactions. 

Redox reactions are a type of chemical reactions that involve the complete or partial transfer of electrons from one atom to another.

Example: On reactant side: Oxidation state of chlorine = -1

                                         Oxidation state of sulphur = 0

On the product side: Oxidation state of chlorine = 0

                             Oxidation state of sulphur = -2

The oxidation state of sulphur reduces from 0 to -2, it is getting reduced and it undergoes reduction reaction. The oxidation state of chlorine increases from -1 to 0. Thus, it is getting oxidized and it undergoes oxidation reaction.

Thus, it is considered as a redox reaction.