This was brought home to me some years ago when I was involved in a small-scale study that used standardised diagnostic instruments with a group of language-impaired children.
For some years she inhabited two completely different worlds of discourse, each using a group of languages that were intratranslatable.
Click languages, a group of languages found only in Africa in which clicks function as normal consonants.
Eastern Sudanic languages, a group of languages representing the most diverse of the major divisions within the Nilo-Saharan language family.
The other two clusters are Na-Dene, a group of languages spoken mostly in Alaska and northeast Canada, and Eskimo-Aleut, spoken across northern Alaska and Canada.
The languages of the Americas, in his view, fell into three major groups, which he named Na-Dene (a group of languages spoken in Alaska and northeastern Canada); Eskimo-Aleut; and Amerind, which included all the other languages.
They say that the only way to prove that a group of languages is related is by establishing regular rules governing how words change as one language morphs into another.
Nilo-Saharan languages, a group of languages that form one of the four language stocks or families on the African continent, the others being Afro-Asiatic, Khoisan, and Niger-Congo.
A further reclassification in terms of genetic affiliation, also made possible as a result of improved knowledge, occurred with respect to a group of languages known as Kadu (or Kadugli-Krongo, formerly Tumtum) spoken in the Nuba Hills of Sudan.
The Indians of Mexico and Central America also still speak languages that date to the time of the Spanish conquest: Uto-Aztecan, a group of languages in central and parts of southern Mexico; the Maya languages, spoken in Yucatan, Guatemala, and adjacent territories; and Oto-Manguean, of central Mexico.
