Wave–particle duality is the principle that light and matter can exhibit both wave-like and particle-like behaviour, with the behaviour observed depending on the experiment performed. Light, for instance, shows interference like a wave but also delivers energy in discrete packets (photons) like particles. The same duality applies to matter, as expressed by the de Broglie relation.

波粒二象性是指光和物质既能表现出波动性又能表现出粒子性的原理,所观察到的行为取决于所进行的实验。例如,光既像波那样发生干涉,又像粒子那样以离散的能量包(光子)传递能量。同样的二象性也适用于物质,由德布罗意关系式表达。