儿化音即“儿”附着在其他字后面时前字和它发音的缩合及改变。通常讨论的儿化音，基于官话或普通话，特指其在音节尾附加-r形式的儿化现象，这也是官话大部份方言具备的发音特点。实际上的儿化音不光指这类产生卷舌元音的现象，如吴语太湖片儿化即作/ŋ/，粤语有的地方又作/n/等。英语某些口音中的r化元音，如/ɚ/和/ɝ/，以及位于元音之后发音的r的发音有时亦俗称“儿化音”。

由于通常的中古汉语拟音中，儿字的声母日母拟作硬颚鼻音类，一些人认为儿化音来自于阿尔泰语系语言。但考察元曲用韵，儿类字皆押入支思韵，显示其时尚未出现儿化音，它可以确证的产生是在明朝汉语自身内部。

Erhua (simplified Chinese:儿化; traditional Chinese:兒化; pinyin:érhuà); also called erhuayin (simplified Chinese:儿化音; traditional Chinese:兒化音; pinyin:érhuàyīn) or erization, refers to a phonological process that adds r-coloring or the "ér" (儿) sound (transcribed in IPA as [ɚ]) to syllables in spoken Mandarin Chinese. It is most common in the speech varieties of North China, especially in the Beijing dialect, as a diminutive suffix for nouns, though some dialects also use it for other grammatical purposes. The Standard Chinese spoken in government-produced educational and examination recordings features erhua to some extent, as in 哪儿 nǎr ("where"), 一点儿 yìdiǎnr ("a little"), and 好玩儿 hǎowánr ("fun"). Colloquial speech in many northern dialects has more extensive erhua than the standardized language. Southwestern Mandarin dialects such as those of Chongqing and Chengdu also have erhua. By contrast, many Southern Chinese who speak non-Mandarin dialects may have difficulty pronouncing the sound or may simply prefer not to pronounce it, and usually avoid words with erhua when speaking Standard Chinese; for example, the three examples listed above may be replaced with the synonyms 哪里 nǎlǐ, 一点 yìdiǎn, 好玩 hǎowán.