In linguistics, the unidirectionality hypothesis proposes that grammaticalisation works in a single direction. That is, pronouns may fuse with verbs, or prepositions may fuse with nouns, to create new inflectional systems, but inflectional endings do not break off to create new pronouns or prepositions.
The unidirectionality hypothesis does not claim that linguistic change will occur in any particular instance, only that if it does occur, it will be in the direction of lexical word to grammatical word and not the other way around.
Certain schools of linguistics object to the unidirectionality hypothesis on theoretical grounds, believing that there should be no favoured direction in the evolution of grammatical forms, and have proposed numerous counter-examples. However, most of these proposals show a lack of understanding of the hypothesis or of the history of the languages in question, and are instead examples of lexicalisation. True counter-examples to unidirectionality appear to be rare and require unusual conditions.
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Famous quotes containing the word hypothesis:
“The hypothesis I wish to advance is that ... the language of morality is in ... grave disorder.... What we possess, if this is true, are the fragments of a conceptual scheme, parts of which now lack those contexts from which their significance derived. We possess indeed simulacra of morality, we continue to use many of the key expressions. But we have—very largely if not entirely—lost our comprehension, both theoretical and practical, of morality.”
—Alasdair Chalmers MacIntyre (b. 1929)