熔点、液化点（M.P.）是在大气压下晶体将其物态由固态转变为液态的过程中固液共存状态的温度；各种晶体的熔点不同，对同一种晶体，熔点又与所受压强有关，压强越大，熔点越高。不过，与沸点不同，熔点受压强的影响很小，因为由固态转变（熔化）为液态的过程中，物质的体积几乎不变化。

进行相反动作（即由液态转为固态）的温度，称之为凝固点、结晶点（对水而言也称为冰点），在一定大气压下，任何晶体的凝固点和熔点相同。习惯上，根据常温（25℃）时物质的状态使用凝固点或熔点称呼这一个温度：对于常温下为固态的物质，这个温度称为熔点；对于常温下为液态的物质，这个温度称为凝固点。

The melting point (or, rarely, liquefaction point) of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard pressure. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point. Because of the ability of some substances to supercool, the freezing point is not considered as a characteristic property of a substance. When the "characteristic freezing point" of a substance is determined, in fact the actual methodology is almost always "the principle of observing the disappearance rather than the formation of ice", that is, the melting point.