The Aztecs () were a Mesoamerican culture that flourished in central Mexico in the post- classic period from 1300 to 1521. The Aztec peoples included different ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl language and who dominated large parts of Mesoamerica from the 14th to the 16th centuries. Aztec culture was organized into city -states (altepetl), some of which joined to form alliances, political confederations, or empires. The Aztec empire was a confederation of three city -states established in 1427, Tenochtitlan, city -state of the Mexica or Tenochca; Texcoco; and Tlacopan, previously part of the Tepanec empire, whose dominant power was Azcapotzalco. Although the term Aztecs is often narrowly restricted to the Mexica of Tenochtitlan, it is also broadly used to refer to Nahua polities or peoples of central Mexico in the prehispanic era, as well as the Spanish colonial era (1521–1821). The definitions of Aztec and Aztecs have long been the topic of scholarly discussion, ever since German scientist Alexander von Humboldt established its common usage in the early nineteenth century.Most ethnic groups of central Mexico in the post- classic period shared basic cultural traits of Mesoamerica, and so many of the traits that characterize Aztec culture cannot be said to be exclusive to the Aztecs. For the same reason, the notion of "Aztec civilization " is best understood as a particular horizon of a general Mesoamerican civilization. The culture of central Mexico includes maize cultivation, the social division between nobility (pipiltin) and commoners (macehualtin), a pantheon ( featuring Tezcatlipoca, Tlaloc and Quetzalcoatl), and the calendric system of a xiuhpohualli of 365 days intercalated with a tonalpohualli of 260 days. Particular to the Mexica of Tenochtitlan was the patron God Huitzilopochtli, twin pyramids, and the ceramic ware known as Aztec I to IV.From the 13th century, the Valley of Mexico was the heart of dense population and the rise of city -states. The Mexica were late-comers to the Valley of Mexico, and founded the city -state of Tenochtitlan on unpromising islets in Lake Texcoco, later becoming the dominant power of the Aztec Triple Alliance or Aztec Empire.
