化合反应是一类化学反应的总称（通常是指无机反应），是指两个或多个反应物经过化学反应生成一种产物。例如，氢气和氧气燃烧生成水就是化合反应。通常化合反应都是放热反应。

1. 2Mg+O₂→2MgO
2. 2H₂+O₂→2H₂O
3. C_(s) +O_2(g)→CO_2(g)

A combination reaction (also known as a synthesis reaction) is a reaction where two or more elements or compounds (reactants) combine to form a single compound (product). Such reactions may be represented by equations of the following form: X + Y → XY.