Abbreviation of attainable region theory.

(linguistics) A particular approach to the architecture of the language organ, based on the principle that the syntactic relation 'X complement of Y' is identical to an inverse-order morphological relation 'X specifier of Y'.

(political science, sociology) Any theory that centres its gaze, analysis, and interpretation around human action. E.g. rational choice theory, phenomenology, etc.

Ideas that are not supported by mainstream scholarship.

(grammar) The original Chomskyan model of generative grammar, based around two different representations of a sentence (deep structure and surface structure) linked by transformational grammar.

(physics) A theory that unifies the electromagnetic interaction, the weak interaction, and the strong interaction.

(chemistry, physics) a theory, a combination of the earlier crystal field theory with molecular orbital theory, that describes the structure of coordination compounds

the theory that changes in prices and the value of money vary with changes in the amount of money in circulation

(astronomy) A mathematical theory that attempts to describe the evolution of the constituents of the universe following the Big Bang

(mathematics, number theory) The branch of number theory in which number-theoretic questions are expressed in terms of properties of algebraic number fields or related objects, and studied using techniques from algebra.