On the Flathead Reservation in northwestern Montana, the sixty remaining fluent speakers of Montana Salish, most of them elderly, speak their language only to each other, changing to English when outsiders or younger tribal members are present. The Aleuts who used to live on Bering Island off the east coast of Russia speak Russian in addition to their native Aleut. The Republic of Singapore, an island nation of just 238 square miles, boasts four official languages. Language contact is everywhere: no nation has a completely monolingual citizenry and many have more than one official language.

Sarah G. Thomason documents the linguistic consequences of language contacts worldwide. Surveying situations in which language contact arises, she focuses on what happens to the languages themselves: sometimes nothing, sometimes the incorporation of new words, sometimes the spread of new sounds and sentence structures across many languages and wide swathes of territory. She outlines the origins and results of contact-induced language change, extreme language mixture―which can produce pidgins, creoles, and bilingual mixed languages―and language death. The book concludes with a brief survey of language endangerment.

Complete with lists of additional readings and references as well as a glossary for students new to the subject, this textbook is a richly documented introduction to a lively, fast-developing field.