Null Subject Parameter

Pro-drop parameter or Null subject parameter is the parameter which determines whether a language is a pro-drop language or not. A positive setting of the parameter allows an empty pro-element to be identified by its governor. This is the case in pro-drop languages.A term used in government-binding theory for a specification of the types of variation that a principle of grammar manifests among different languages. It is suggested that there are no rules of grammar in the traditional sense, but only principles which can take a slightly different form in different languages. For example, a head parameter specifies the positions of heads within phrases (e.g. head-first in English, head-last in Japanese). The adjacency parameter of case theory specifies whether case assigners must be adjacent to their noun phrases (e.g. to the left in English, to the right in Chinese). The pro-drop (or ‘null subject’) parameter determines whether the subject of a clause can be suppressed. Determining the parametric values for given languages is known as parameter-setting. The overall approach has been called the principles and parameters theory (PPT) of universal grammar, and has since come to be applied outside of syntactic contexts, notably in characterizing phonological relations. Later versions of metrical phonology, for example, recognize a series of parameters governing the way metrical feet should be represented, such as quantity sensitivity and directionality.