Nan oxidation-reduction reaction, oxidation is what happens when a reactant . reduction occurs when a reactant in the reaction.

Oxidation occurs when a reactant loses electrons during the reaction. Reduction occurs when a reactant gains electrons during the reaction. This often occurs when metals are reacted with acid.

Answer : Oxidation reaction occurs when a reactant losses electrons in the reaction.

Reduction reaction occurs when a reactant gains electrons in the reaction.

Explanation :

Redox reaction or Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.

Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. That means, the loss of electrons takes place.

Or we can say that, oxidation reaction occurs when a reactant losses electrons in the reaction.

Reduction reaction : It is defined as the reaction in which a substance gains electrons. That means, the gain of electrons takes place.

Or we can say that, reduction reaction occurs when a reactant gains electrons in the reaction.