The present book, an updated and expanded version of the volume English Phonology: Variation and Comparison (Forchini 2010), focuses on the phonological system of American English (henceforth AmE), namely, the variety of English which was originally spoken only in the United States of America (cf. Map 1), but which has nowadays become the speaking model of many other countries in the world. The aim is to describe the phonological variation that characterizes AmE and distinguishes it from other Englishes by starting from the assumption that it is the phonological level of language which plays a crucial role in distinguishing varieties (Bauer 2002:69). The differences related to speaking are, indeed, much larger than those related to writing (Tottie 2002, Trudgill and Hannah 2002). As pointed out by Bauer (2002:69), it is on the basis of pronunciation that “we are willing to place almost any speaker in the English-speaking world”. Indeed, we can usually tell after just a few words whether someone has a Scottish, Australian or American accent without needing to wait for them to say some particularly revealing local word or to use some special construction (Bauer 2002:2-3). Being aware of the phonological differences which characterize language varieties is, then, a fundamental step toward reaching mastery of English.