Routledge Dictionary of Language and Linguistics.pdf

Dictionary of language and linguistics 1296XX-bar theory (also X-bar syntax)A theoretical concept in transformational grammar which restricts the form ofcontextfree phrase structure rules. This theory was developed by Chomsky (1970) andJackendoff (1977) on the following premises: (a) all syntactically complex categories ofall natural languages (NP, VP, PP, etc.) are formed according to universal structuralprinciples; (b) all lexical categories can be defined according to a limited inventory ofsyntactic features like [±N] and [±V], e.g. verb=[+V, −N], noun=[−V, +N],adjective=[+V, +N], preposition=[−V, −N]; (c) a distinction can be made between thelevels of complexity within phrases, such that phrases themselves (NPs, VPs, PPs) aremaximally complex categories of the type N, V, P. Lexical categories of the type N, V, Pare minimally complex. There is another level of complexity which falls between thesetwo. The phrase the House of Commons [det N PP] is maximally complex because itcannot be expanded further as an NP. House [N] is minimally complex, while House ofCommons [N PP] belongs to an intermediate category. The whole phrase can be denotedusing the notation N 2 , N″, or; this level of projection is also referred to as NP.House Nº N NHouse of Commons N 1 N′The House of Commons N 2 N″Every possible phrase structure rule is derived from X in the general form X i […X j …],where (i) the dots stand for any number of categories of maximal complexi ty, and (ii) theindices i and j stand for the level of complexity of the category X and (iii) X j cannot bemore complex than X i . Phrase structure rules like VP→A NP are ruled out by theseconstraints. The term ‘X-bar’ arises from the notation where one or more bars are placedabove the constituent X to represent the levels of complexity. For that reason, thefollowing notation may be used: X, X′, X″, X 0 , X 1 , X 2 , or X, , where the maximalprojection can also be referred to as XP.