X-bar theory

noun

A theory that posits a common syntactic structure for different lexical categories. Each phrase (XP) is the projection of a head (X) and may optionally include a specifier (sister of X-bar, daughter of XP), adjuncts (sister and daughter of X-bar) and complements (sister of X, daughter of X-bar).

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Meanings

nounX-bar theory (uncountable)

alternative X′ theory

  1. uncountablehuman sciencesA theory that posits a common syntactic structure for different lexical categories. Each phrase (XP) is the projection of a head (X) and may optionally include a specifier (sister of X-bar, daughter of XP), adjuncts (sister and daughter of X-bar) and complements (sister of X, daughter of X-bar).

Origin

X signifies an arbitrary lexical category; certain structures are represented by this letter and an overbar.

Full word history & related roots →

Translations

Chinese Mandarin X槓理論 /X杠理论, X階理論 /X阶理论
  • X槓理論 /X杠理论 (X-gàng lǐlùn)theory
  • X階理論 /X阶理论 (X-jiē lǐlùn)theory
  • X標槓理論 /X标杠理论 (X-biāogàng lǐlùn)theory
French théorie X-barre
  • théorie X-barretheory
Polish teoria X-bar
  • teoria X-bartheory
Russian X-штрих-теория
  • X-штрих-теория (X-štrix-teorija)theory
Cite this entry
APA

X-bar theory. (n.d.). In WatkinsX Dictionary. Retrieved November 5, 2026, from https://dictionary.watkinsx.com/word/X-bar%20theory

MLA

“X-bar theory.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/X-bar%20theory. Accessed November 5, 2026.

Chicago

WatkinsX Dictionary, s.v. “X-bar theory,” accessed November 5, 2026, https://dictionary.watkinsx.com/word/X-bar%20theory.

Source: X-bar theory on Wiktionary, CC BY-SA 4.0.