About Nahuatl Language
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.
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.