同形词是指写法相同，但意义不同的词语。

例如英文的 bear 当作为名词时解作「熊」，但当作为动词时则解作「忍受」或「揹着」。

有时不同的语文也会有同形词，例如「real」对同样使用拉丁字母的西班牙文和英文就有不同意义，前者解作「皇家」、后者则解作「真」；「勉强」对同样使用汉字的日文和中文也有不同意义。

A homograph (from the Greek:ὁμός, homós, "same" and γράφω, gráphō, "write") is a word that shares the same written form as another word but has a different meaning. However, some dictionaries insist that the words must also sound differently, while the Oxford English Dictionary says that the words should also be of "different origin". In this vein, The Oxford Guide to Practical Lexicography lists various types of homographs, including those in which the words are discriminated by being in a different word class, such as hit, the verb to strike, and hit the noun a blow.