Alan S. Kaye
Although the French term diglossie was introduced by the Arabist William Marc°ais in 1930 (Marc°ais 1930), it is the late Charles A. Ferguson who is most often credited as the first to introduce the notion of a ``high'' (H) and a ``low'' (L) variety or register of a language in a classic (1964 [1959]) article in the journal Word with the now famous one-word title, ``Diglossia.'' The gist of his widely influential essay was to demonstrate that the idea of H and L registers best explained the pervasive linguistic distinctions observable in a few speech communities concerning the strict complementary distribution of formal vs. informal usage. For Ferguson, who calqued the term from the French, there were only four ``defining'' languages that he considered representative: Arabic, Swiss German, Haitian Creole, and Modern Greek. This essay reviews some of the voluminous diglossia literature and focuses on the linguistic situation in the Arab world, presenting ideas about future research prospects (such as the diglossic continuum).