The Songhai (also Songhay or Sonrai) are west Africans who speak Songhai languages, the lingua franca of the Songhai Empire which dominated the western Sahel in the 15th and 16th century. The Songhai are found primarily throughout Mali in the Western sudanic region (not the country). The name Songhai is historically neither an ethnic nor a linguistic designation, but a name for the ruling caste of the Songhay Empire. Speakers in Mali have adopted it as an ethnic self-designation but other Songhay-speaking groups identify themselves by other ethnic terms such as Zarma (or Djerma, the largest subgroup of the Songhai) or Isawaghen. The dialect of Koyraboro Senni spoken in Gao is unintelligible to speakers of the Zarma dialect of Niger, according to at least one report. The Songhay languages are commonly taken to be Nilo-Saharan but this classification remains controversial: Dimmendaal (2008) believes that for now it is best considered an independent language family.