General Aztec

Nahuan
Aztecan
Region	El Salvador and Mexico: México (state), Distrito Federal, Puebla, Veracruz, Hidalgo, Guerrero, Morelos, Oaxaca, Michoacán and Durango
Native speakers	1.5 million (2010 census)
Language family	Uto-Aztecan Nahuan
Official status
Regulated by	Instituto Nacional de Lenguas Indígenas
Language codes
ISO 639-2
ISO 639-3	Variously: nci – Classical Nahuatl nhn – Central Nahuatl nch – Central Huasteca Nahuatl ncx – Central Puebla Nahuatl naz – Coatepec Nahuatl nln – Durango Nahuatl nhe – Eastern Huasteca Nahuatl ngu – Guerrero Nahuatl azz – Highland Puebla Nahuatl nhq – Huaxcaleca Nahuatl nhk – Isthmus-Cosoleacaque Nahuatl nhx – Isthmus-Mecayapan Nahuatl nhp – Isthmus-Pajapan Nahuatl ncl – Michoacán Nahuatl nhm – Morelos Nahuatl nhy – Northern Oaxaca Nahuatl ncj – Northern Puebla Nahuatl nht – Ometepec Nahuatl nlv – Orizaba Nahuatl ppl – Pipil language nhz – Santa María la Alta Nahuatl npl – Southeastern Puebla Nahuatl nhc – Tabasco Nahuatl nhv – Temascaltepec Nahuatl nhi – Tenango Nahuatl nhg – Tetelcingo Nahuatl nuz – Tlamacazapa Nahuatl nhw – Western Huasteca Nahuatl nsu – Sierra Negra Nahuatl xpo – Pochutec
Glottolog	azte1234
Map showing the areas of Mesoamerica where Nahuatl dialects are spoken today (white) and where it is known to have been spoken historically (grey)

The Nahuan or Aztecan languages are those languages of the Uto-Aztecan language family that have undergone a sound change, known as Whorf's Law, that changed an original *t to /tɬ/ before *a. Subsequently, some Nahuan languages have changed this /tɬ/ to /l/ or back to /t/, but it can still be seen that the language went through a /tɬ/ stage. The best known Nahuan language is Nahuatl.

Some authorities, such as the Mexican government, Ethnologue, and Glottolog, consider the varieties of modern Nahuatl to be distinct languages, because they are often mutually unintelligible and their speakers have distinct ethnic identities. As of 2008, the Mexican government recognizes thirty varieties that are spoken in Mexico as languages (see the list below).

Researchers distinguish between several dialect areas that each have a number of shared features: One classification scheme distinguishes innovative central dialects, spoken around Mexico City, from conservative peripheral ones spoken north, south and east of the central area, while another scheme distinguishes a basic split between western and eastern dialects. Nahuan languages include not just varieties known as Nahuatl, but also Pipil and the extinct Pochutec language. The distinction between the Nahuatl and Pochutec is now thought to be due to language contact; see Pochutec language for details.

The differences among the varieties of Nahuatl are not trivial, and in many cases result in low or no mutual intelligibility: people who speak one variety cannot understand or be understood by those from another. Thus, by that criterion, they could be considered different languages. The ISO divisions referenced below respond to intelligibility more than to historical or reconstructional considerations. Like the higher-level groupings, they also are not self-evident and are subject to considerable controversy.