Principles and parameters is a framework within generative linguistics in which the syntax of a natural language is described in accordance with general principles (i.e. abstract rules or grammars) and specific parameters (i.e. markers, switches) that for particular languages are either turned on or off. For example, the position of heads in phrases is determined by a parameter. Whether a language is head-initial or head-final is regarded as a parameter which is either on or off for particular languages (i.e. English is head-initial, whereas Japanese is head-final). Principles and parameters was largely formulated by the linguists Noam Chomsky and Howard Lasnik. Many linguists have worked within this framework, and for a period of time it was considered the dominant form of mainstream generative linguistics.
Principles and parameters as a grammar framework is also known as government and binding theory. That is, the two terms principles and parameters and government and binding refer to the same school in the generative tradition of phrase structure grammars (as opposed to dependency grammars). However, Chomsky considers the term misleading.
