Two languages can resemble each other in the categories, constructions, and types of meaning they use; and in the forms they employ to express these. Such resemblances may be the consequence of universal characteristics of language, of chance or coincidence, of the borrowing by one language of another's words, or of the diffusion of grammatical, phonetic, and phonological characteristics that takes place when languages come into contact. Languages sometimes show likeness because they have borrowed not from each other but from a third language. Languages that come from the same ancestor may have similar grammatical categories and meanings expressed by similar forms: such languages are said to be genetically affiliated. This book considers how and why forms and meanings of different languages at different times may resemble one another. Its editors and authors aim (a) to explain and identify the relationship between areal diffusion and the genetic development of languages, and (b) to dis