Library science

Separable space

Natural language

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Universal grammar

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Generative grammar

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Natural number

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Mildly context-sensitive grammar formalism

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Language

This article proposes that the possible word orders for any natural language construction composed of n elements, each of which selects for the category headed by the next, are universally limited both across and within languages to a subclass of permutations on the ‘universal order of command’ 1, …, n, as determined by their selectional restrictions. The permitted subclass is known as the ‘separable’ permutations, and grows in n as the large Schröder series {1, 2, 6, 22, 90, 394, 1806, … }. This universal is identified as formal because it follows directly from the assumptions of combinatory categorial grammar (CCG)—in particular, from the fact that all CCG syntactic rules are subject to a combinatory projection principle that limits them to binary rules applying to contiguous nonempty categories.

A formal universal of natural language grammar