Answer :
Oxidation :The reaction in which a substance gains oxygen is called oxidation. e.g. when oxygen is added to copper it forms copper oxide. \( 2Cu + O_{2}\rightarrow 2CuO \) Reduction:The reaction in which a substance loses oxygen is called Reduction. e.g. when Hydrogen gas passed over the heated copper oxide it formed copper along with water. \( CuO+ H_{2}\rightarrow Cu+H_{2}O\)