X-bar theory = X-bar syntax

X-bar theory (= X-bar syntax) is a linguistic postulate according to which all phrases and sentences in languages are structured according to a certain (syntactic) model; this model can be made explicit through a linguistic analysis and consequently can be depicted graphically with the help of strictly hierarchical diagrams.

The X-bar theory was developed within generative (transformational) grammar. Its “generative” character is shown in that 1) all grammatically correct phrases or sentences are assumed to be structured according to certain principles (rules) and 2) all languages are assumed to have similar basic principles or rules.

Chomsky (1970) and Jackendoff (1977) are considered to be the founders of the X-bar theory.

Below is an example (see the end of the post for the explanations) of a phrase analyzed with the help of the X-bar theory.


X-bar theory conventions (terminology, abbreviations, and symbols/labelling):

  • X is the head (hence, X-bar) – the core of the whole syntactic structure. The letter X is substituted with what is appropriate in a given case (e.g. N for a noun + see below);
  • comp = complement – a word or several words which are necessary to the head to complete its meaning: direct object (e.g. read books), indirect object (e.g. smile at friends);
  • adjt = adjunct – a word or several words which modify the head, but do not make a sentence ungrammatical if they are removed from it: an adjective (e.g. wise, yellow), an adverb (e.g. kindly, quickly), a prepositional phrase (e.g. a spoon of wood);
  • spec = specifier – a word or several words which qualify/determine/specify the head: articles (e.g.  a book, the book), possessive determiners (e.g. my house), demonstrative determiners (e.g. this student, that professor, those gentlemen), quantifiers (e.g. every winter, some assignments), intensifiers (e.g. very interesting, quite serious);
  • XP = X-phrase = X-double-bar = X-bar-bar =  X''-2 = X” = X2 – the maximal projection (i.e. the topmost node) of a head X;
  • XB = X-bar – the general term for any of the intermediate projections derived from X (e.g. VB is an intermediate projection of V).

A = adverb (e.g. quickly, kindly);
C = conjunction (e.g. and, but);
D = determiner (e.g. a, the, my, every winter);
I = auxiliary verb (e.g. has been reading);
J = adjective (e.g. beautiful, yellow);
N = noun or a nominal (e.g. I, Tom, table);
P = preposition (e.g. on, in);
V = verb (e.g. go, live).

Example explained:
“they” is a NP – a maximal projection of a nominal head (pronoun “they”). It is the specifier of the VP;
“cooked” is the head of the VP, which is a projection of it;
“the cabbage” is a NP – a maximal projection of a nominal head (noun “cabbage”). It is the complement of the VP and, thus, constitutes a VB;
“the” is a D, – a maximal projection of a determiner head (article “the”). It is the specifier of the NP, which is inside the VB;
“yesterday” is an AP – a maximal projection of an adverbial head (adverb “yesterday”). It is the adjunct of the VP and, thus, constitutes a VB;
VP, NP, DP, AP – maximal projections;
VB and NB – intermediate projections.

Chomsky, N. (1970). Remarks on nominalization. In R. A. Jacobs and P. S. Rosenbaum (eds), Readings in English transformational grammar (pp. 170–221). Waltham, MA: Ginn and Company.
Jackendoff, R. (1977). Constraints on phrase structure rules. In P. W. Culicover, T. Wasow, and A. Akmajian (eds), Formal syntax (pp. 249–283). New York: Academic Press.
— (1977). X-bar syntax: a study of phrase structure. Cambridge, MA: MIT Press.



  1. RC

    Reblogged this on Grammaticism.

  2. Abdul-Majeed

    I need more help since I’m doing grammar at the Mphil level. Any help or books will be highly welcome

    • Hi Abdul!
      The sources that I can think of are:
      1) Johansson, M., and Manninen, M. (2012). English linguistics: introduction to morphology, syntax and semantics. Lund: Studentlitteratur.
      This source may help you to understand certain concepts better.

      Since you are a university student, you should be able to access the following databases:
      2) Dissertation Abstracts see ProQuest Dissertations and Theses (published theses)
      3) Linguistics and Language Behavior Abstracts (scholarly articles)
      4) Ebrary (electronic books online)
      Sources 2, 3, and 4 may help you to find more advanced information which can be of help in your own research. In order to take advantage of these databases you have to use your university library website. Good luck in your studies!

      Does anybody else have useful information/good sources on the topic? Thanks!


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