A decomposition reaction is a reaction in which a single reactant splits into two or more products. It is the opposite of a combination reaction and often requires an input of energy as heat or electricity. The breakdown of calcium carbonate into calcium oxide and carbon dioxide on heating is an example of a decomposition reaction.

分解反应是一种反应物分裂为两种或多种产物的反应。它与化合反应相反,通常需要以热或电的形式输入能量。碳酸钙受热分解为氧化钙和二氧化碳就是分解反应的一个例子。