A combination reaction is a reaction in which two or more substances combine to form a single product. It is the opposite of a decomposition reaction, in which one substance breaks apart into several. The formation of magnesium oxide from magnesium and oxygen is an example of a combination reaction.

化合反应是两种或多种物质结合生成一种产物的反应。它与一种物质分裂为多种产物的分解反应相反。镁与氧生成氧化镁就是化合反应的一个例子。