在语法中，转换是一种句法规则或惯例，可以将句子中的一个元素从一个位置移动到另一个位置。它来源于拉丁语“跨越形式”，发音为“trans代表五月顺”。它也被称为T形规则

观察

诺姆·乔姆斯基（Noam Chomsky）在《句法理论的各个方面》（Aspects of the Theory of Syntax）中写道，“转换是通过它所应用的结构分析以及它对这些字符串的结构变化来定义的。”其他作者、语言学家和语法学家对该术语的描述如下：

"In traditional grammar, the concept of transformation was used mainly as a didactic means for developing the appropriate linguistic habits.... "The credit for making the concept of transformation popular and significant belongs primarily to Zellig S. Harris and Noam Chomsky....Harris introduced the concept of transformation to linguistics in order to reinforce the effectiveness of the method of reducing utterances to certain basic sentence structures."

–Kazimierz Polanski，“关于转换的一些评论”，《跨越历史和地理边界的语言学》，D.Kastovsky等人主编，Walter de Gruyter，1986年

"Some of [Noam] Chomsky's notation, and some of his terminology too--including transform itself, defined in part by the Random House Dictionary as 'changing the form of (a figure, expression, etc.) without in general changing the value' -- have a distinctly mathematical air about them. . . . [But] TG [transformational grammar] is not a mathematical grammar. The processes it describes are not mathematical processes and the symbols it describes are not used with their mathematical meaning. "Chomsky's grammar is a 'generative grammar of the transformational type.' By that he means that it makes explicit the rules for generating new sentences, not for analyzing existing sentences; the rules themselves provide the analysis. And he means that among the rules are those for transforming one type of sentence into another (affirmative into negative, simple into compound or complex, and so forth); the transformations make the relationships among such sentences clear."

——W.F.博尔顿，一种活的语言：英语的历史和结构。兰登书屋，1982年

转换示例

“被动代词删除。在许多情况下，我们在被动句中删除代词，如第6:6句。蛋糕被吃掉了。当主语代词不确定时，我们使用不定代词来填补它在深层结构中出现的位置，如6a:6a。[某人]吃蛋糕。然而，这种深层结构会导致6b:6b的表面结构。蛋糕被人吃了为了解释第6句，T-G语法提出了一个删除规则，删除了包含主语成分的介词短语。因此，我们可以说，该句子经历了两种转换，被动和被动成分删除。”——詹姆斯·戴尔·威廉姆斯，《教师语法书》，第二版。劳伦斯·厄尔鲍姆，2005年