Navajo or Navaho (native name: Diné bizaa) is an Athabaskan language (of Na-Dené stock) spoken in the southwest United States by the Navajo people (Diné). It is geographically and linguistically one of the Southern Athabaskan languages (the majority of Athabaskan languages are spoken in northwest Canada and Alaska). Navajo claims more speakers than any other Native American or First Nation language north of the U.S.-Mexico border, with more than 100,000 native speakers, and this number has actually increased with time. During World War II, a code based on Navajo was used by code talkers to send secure military messages over radio.