Aztec is a term used to refer to certain ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl language and who achieved political and military dominance over large parts of Mesoamerica in the 14th, 15th and 16th centuries, a period referred to as the Late post-Classic period in Mesoamerican chronology. Often the term "Aztec" refers exclusively to the people of Tenochtitlan, situated on an island in Lake Texcoco, who called themselves Mexica Tenochca or Colhua-Mexica. Sometimes also includes the inhabitants of Tenochtitlan's two principal allied city-states, the Acolhuas of Texcoco and the Tepanecs of Tlacopan, who together with the Mexica formed the Aztec Triple Alliance which has also become known as the "Aztec Empire". In other contexts it may refer to a..