How to define endothermic and exothermic reactions?

To correctly distinguish these reactions, you need to know the definitions. 1) Endothermic reaction – reactions proceeding with the absorption of heat (To get a reaction, you need to add energy to it: light or fire). 2) Exothermic reaction – a reaction proceeding with the release of heat (here, on the contrary, the reaction releases energy or heat). all reactions of combustion, oxidation, compounds of metals with other elements, etc. are exothermic.
Endothermic reactions are many decomposition reactions.