同音词是指语言中读音相同，但是意义不同的词汇。在汉语，由于汉字的特殊性，因此还有同音字，也就是读音相同，但是意义不同的汉字。

由于文本的书写形式问题，有人还把同音词分成两种：

虽然同音词可能会在交谈时引起词义混淆，但是在具体的语言环境里，配合上下文、手势、声调等，很少真正会引起混淆。同音词也是文本游戏、修辞、猜谜等常用的元素之一。

In linguistics, a homonym is one of a group of words that share the same pronunciation but have different meanings, whether spelled the same or not. A more restrictive definition sees homonyms as words that are simultaneously homographs (words that share the same spelling, regardless of their pronunciation) and homophones (words that share the same pronunciation, regardless of their spelling). The relationship between a set of homonyms is called homonymy. Examples of homonyms are the pair stalk (part of a plant) and stalk (follow/harass a person) and the pair left (past tense of leave) and left (opposite of right). A distinction is sometimes made between "true" homonyms, which are unrelated in origin, such as skate (glide on ice) and skate (the fish), and polysemous homonyms, or polysemes, which have a shared origin, such as mouth (of a river) and mouth (of an animal).