Whorf's law is a sound law in Uto-Aztecan linguistics proposed by the linguist Benjamin Lee Whorf. It explains the origin in the Nahuan languages of the phoneme /tɬ/ which is not found in any of the other languages of the Uto-Aztecan family. The existence of /tɬ/ in Nahuatl had puzzled previous linguists and caused Sapir to reconstruct a /tɬ/ phoneme for Proto-Uto-Aztecan based only on evidence from Aztecan. In a 1937 paper published in the journal American Anthropologist, Whorf argued that phoneme was a result of some of the Nahuan or Aztecan languages having undergone a sound change changing the original */t/ to [tɬ] in the position before */a/. This sound law has come to be known as "Whorf's law", and is still considered valid although a more detailed understanding of the precise conditions under which it took place has been developed. The situation had been obscured by the fact that oftentimes the */a/ had then subsequently been lost or changed to another vowel, making it difficult to realize what had conditioned the change. Because some Nahuan languages have /t/ where others have /tɬ/, Whorf thought that the law had been limited to certain dialects and that the dialects that had /t/ were more conservative. In 1978, Lyle Campbell and Ronald Langacker showed that in fact Whorf's law had affected all of the Nahuan languages and that some dialects had subsequently changed /tɬ/ back to /t/. In 1996, Alexis Manaster Ramer showed that the sound change had in fact also happened before the Proto-Uto-Aztecan high central vowel */ɨ/, and not just before */a/.
- Campbell, Lyle; Langacker, Ronald (1978). "Proto-Aztecan vowels: Part I". International Journal of American Linguistics (Chicago: University of Chicago Press) 44 (2): 85–102. doi:10.1086/465526. OCLC 1753556.
- Canger, Una (1988). "Nahuatl dialectology: A survey and some suggestions". International Journal of American Linguistics (Chicago: University of Chicago Press) 54 (1): 28–72. doi:10.1086/466074. OCLC 1753556.
- Launey, Michel (1996). "Retour au -tl aztèque". Amerindia 21: 77–91.
- Manaster Ramer, Alexis (1996). "On Whorf's Law and Related Questions of Aztecan Phonology and Etymology". International Journal of American Linguistics 62 (2): 176–187. doi:10.1086/466285.
- Whorf, Benjamin Lee (1937). "The origin of Aztec tl". American Anthropologist 39 (2): 265–274. doi:10.1525/aa.1937.39.2.02a00070.