ABSTRACT
A constraint on transformational rules ( transformation) for the situation in which coreferential constituents would be crossed over. This could occur, for example, in the movement of a wh-element in COMP position over a co-indexed pronoun. In accordance with the current grading of ungrammaticality, one can distinguish between weak crossover and strong cross-over. Thus *Whoi does his1 mother love ti (weak cross-over) is clearly more acceptable than *Whoi did hei love t1 or *Who, did hei say Caroline kissed ti (strong cross-over). The cross-over principle has been the center of interest for many in generative grammar since the early 1970s. In Government and Binding theory, it is simply a descriptive term and relevant cases must be explained by general principles and parameters of the syntactic theory. An example of this would be the assimilation of the empty category ( empty category principle) left by wh-movement to independently referential expressions where principle C of the binding theory would be relevant; as a result the strong cross-over phenomena would be excluded from the grammar, since the pronoun would be excluded from binding the empty category.
