The Mixtec (ˈmiːstɛk,_ˈmiːʃtɛk) languages belong to the Mixtecan group of the Oto-Manguean language family. Mixtec is spoken in Mexico and is closely related to Trique and Cuicatec. The varieties of Mixtec are spoken by over half a million people. Identifying how many Mixtec languages there are in this complex dialect continuum poses challenges at the level of linguistic theory. Depending on the criteria for distinguishing dialects from languages, there may be as few as a dozen or as many as fifty-three Mixtec languages. The name "Mixteco" is a Nahuatl exonym, from mixtecatl, from mixtli miʃ.t͡ɬi ("cloud") + -catl kat͡ɬ ("inhabitant of place of"). Speakers of Mixtec use an expression (which varies by dialect) to refer to their own language, and this expression generally means "sound" or "word of the rain": dzaha dzavui in Classical Mixtec; or "word of the people of the rain", dzaha Ñudzahui (Dzaha Ñudzavui) in Classical Mixtec. Denominations in various modern Mixtec languages include tu'un savi tũʔũ saβi, tu'un isasi [tũʔũ isasi] or isavi [isaβi], tu'un va'a [tũʔũ βaʔa], tnu'u ñuu savi [tnũʔũ nũʔũ saβi], tno'on dawi [tnõʔõ sawi], sasau [sasau], sahan sau [sãʔã sau], sahin sau [saʔin sau], sahan ntavi [sãʔã ndavi], tu'un dau [tũʔũ dau], dahan davi [ðãʔã ðaβi], dañudavi [daɲudaβi], dehen dau [ðẽʔẽ ðau], and dedavi [dedavi]. The traditional range of the Mixtec languages is the region known as La Mixteca, which is shared by the states of Oaxaca, Puebla and Guerrero. Because of migration from this region, mostly as a result of extreme poverty, the Mixtec languages have expanded to Mexico's main urban areas, particularly the State of México and the Federal District, to certain agricultural areas such as the San Quintín valley in Baja California and parts of Morelos and Sonora, and into the United States. In 2012, Natividad Medical Center of Salinas, California had trained medical interpreters bilingual in Mixtec as well as in Spanish; in March 2014, Natividad Medical Foundation launched Indigenous Interpreting+, "a community and medical interpreting business specializing in indigenous languages from Mexico and Central and South America," including Mixtec, Trique, Zapotec, and Chatino.