Isthmus Zapotec (autoglossonym: [dìʤàˈzàˑ]) is the common name used for a variety of Zapotec (Otomanguean family) spoken on the Isthmus of Tehuantepec, Oaxaca, Mexico (Suárez 1983: xvi; Campbell 1997: 158). It is now officially listed by the Instituto Nacional de Lenguas Indígenas (INALI 2008) as ‘zapoteco de la planicie costera’ (‘coastal plain Zapotec’) to distinguish it from other varieties of Zapotec spoken on the Isthmus. It is the mother tongue of many inhabitants of various cities and towns, as well as many smaller communities (INALI 2008), with some lexical, syntactic and phonetic variation between towns only a few kilometers apart. The ISO 639-3 code for this variety is zai. Since the most recent census figures do not separate out the varieties of Zapotec, and have not done so reliably when attempted, official statistics as to the number of speakers of Isthmus Zapotec are not available. (The Ethnologue (Lewis 2009) cites the 1990 census as listing 85,000 speakers; that figure must have been an interpretation of other statistics in the census.) INALI (personal communication, September 2008) estimates the current number to be about 104,000. In the city of Tehuantepec, the language is no longer widely used. In certain other locations, including Juchitán de Zaragoza, Spanish is becoming the dominant or the only language spoken by many people born after about 1990, although Zapotec is dominant in many outlying towns, including San Blas Atempa. Mature speakers have remarked that young people who are not fluent do not use tones correctly. Isthmus Zapotec has had active writers, including poets and novelists, since the first half of the twentieth century, well before an orthography was officially established (Alfabeto popular 1956), but reading and writing of the language are still not taught in schools in the region.