同化(assimilation)或者语音同化为语言学里面语音规则(Phonological rule/语音流变)的一种。系指一个语音受到环境影响，而变得加快影响其本有之语音的现象；通常在讲话速度快时候出现，但不一定会如此。

语音同化可以是一种共时现象，亦可以是一种历时现象。一个语音可能会受到后面语音、前面语音、或者另外一个语音、甚至来自环境的影响，而同化其原有之语音。

In phonology, assimilation is a common phonological process by which one sound becomes more like a nearby sound. This can occur either within a word or between words. In rapid speech, for example, "handbag" is often pronounced [ˈhæmbæɡ]. As in this example, sound segments typically assimilate to a following sound (this is called regressive or anticipatory assimilation), but they may also assimilate to a preceding one (progressive assimilation). While assimilation most commonly occurs between immediately adjacent sounds, it may occur between sounds separated by others ("assimilation at a distance").