Define Exothermic and Endothermic Reaction?

"Exo" means releases and "thermic" means heat.

An exothermic reaction is a chemical reaction that releases energy through light or heat

It is expressed in a chemical equation: reactants → products + energy.

"Endo" means absorbing and "thermic" means heat.

An Endothermic Reaction is a chemical reaction in which energy is absorbed in the form of light or heat.

It is expressed in a chemical equation: Reactants + Heat --> Products.