In linguistic circles, there is much discussion over the definitions of language and dialect. It may be generalized that a language is made up of dialects, which are simply regional variants of the same tongue, but even here there is controversy. What about Chinese, a language spoken by millions in the world’s largest country? Among the Chinese dialects, some have drifted so far that mutual comprehension is no longer possible. Serbian and Croatian may also be considered, which although by all outward appearances may be considered one language, are spoken by two countries separated by religion and orthography.
So where do you draw the line? When does a dialect cease its dependence and become a full-fledged language? While I was among the Aztecs in San Luis Potosí, Mexico, I heard yet another explanation from a bilingual preacher there.
Nahuatl, he said, is not a language like Spanish or English, because of its variability. He cited two synonymous words in Nahuatl, the one being used only in that place, and the other heard in another village. In short, I believe he was essentially pointing out the disunity among the many variants of Nahuatl. Whereas English and Spanish both have standard forms understood by everyone, no such form of Nahuatl exists, only many different accents and differences in vocabulary across Mexico. Thus, when referring to Nahuatl in Spanish, the Mexicans will say el dialecto náhuatl instead of using the word idioma or lengua.
So there you have it, straight from the horse’s mouth. Personally, I would consider Nahuatl as a language and its variants as dialects, but in Spanish I will refer to it as a dialect, for “when in Mexico, do as the Mexicans do.”