* Combustion: A chemical process involving rapid reaction between a substance with an oxidant, usually oxygen, producing heat and light.

* In this reaction:

* Sulfur dioxide (SO2) reacts with oxygen (O2).

* Heat and light are released (although the amount of light may be less noticeable).

* The products are sulfur trioxide (SO3), a new compound formed by the combination of reactants.

Therefore, all the criteria for a combustion reaction are met.