in descriptive linguistics and traditional grammar, the formation of a word by changing the form of the base or by adding affixes to it. In this sense, derivation is also called “word formation.” In historical linguistics, the derivation of a word is its history and etymology. In generative grammar, derivation means a sequence of linguistic representations that indicate the structure of a sentence or other linguistic unit before, during, and after the application of some grammatical rule or set of rules.