Allan Metcalf is the world's leading expert on the history and meaning of OK (or okay), America's greatest and most successful word. He has also studied the history and development of many other words of English and has published his findings in six books aimed at the general reader (see Books), the most recent being OK: The Improbable Story of America's Greatest Word (Oxford University Press, 2010). That book was accorded a full-page review in The New York Times Book Review and earned this accolade in the journal of the Dictionary Society of North America: "The book is full of life, highly readable, a page-turner. . . . It is a sterling example of what linguistic scholarship can, and should, be for the general reader."
He has used his expertise assisting attorneys and law enforcement officials in matters of forensic linguistics, including determining the meaning of worlds in their historical and grammatical context and dealing with authorship identification, libel, and copyright.
Since 1981 he has been executive secretary of the American Dialect Society, a scholarly association for the study of the English language in North America. He is professor of English and chair of the Division of Humanities and Fine Arts at MacMurray College.