Paul J. Hopper, Elizabeth Closs Traugott. Grammaticalization. New York, Cambridge University Press, 2003.

Grammaticalization refers to the change whereby lexical terms and constructions serve grammatical functions in certain linguistic contexts and, once grammaticalized, continue to develop new grammatical functions. Paul Hopper and Elizabeth Traugott synthesize research from several areas of linguistics in this revised introduction to the subject. The book includes substantial updates on theoretical and methodological issues that have arisen in the decade since the first edition, as well as a significantly expanded bibliography.