group of languages that once covered and today still partially cover all of South America, the Antilles, and Central America to the south of a line from the Gulf of Honduras to the Nicoya Peninsula in Costa Rica. Estimates of the number of speakers in that area in pre-Columbian times vary from 10,000,000 to 20,000,000. In the early 1980s there were approximately 15,900,000, more than three-fourths of them in the central Andean areas. Language lists include around 1,500 languages, and figures over 2,000 have been suggested. For the most part, the larger estimate refers to tribal units whose linguistic differentiation cannot be determined. Because of extinct tribes with unrecorded languages, the number of languages formerly spoken is impossible to assess. Only between 550 and 600 languages (about 120 now extinct) are attested by linguistic materials. Fragmentary knowledge hinders the distinction between language and dialect and thus renders the number of languages indeterminate.

Because the South American Indians originally came from North America, the problem of their linguistic origin involves tracing genetic affiliations with North American groups. To date only Uru-Chipaya, a language in Bolivia, is surely relatable to a Macro-Mayan phylum of North America and Mesoamerica. Hypotheses about the probable centre of dispersion of language groups within South America have been advanced for stocks like Arawakan and Tupian, based on the principle (considered questionable by some) that the area in which there is the greatest variety of dialects and languages was probably the centre from which the language groups dispersed at one time; but the regions in question seem to be refugee regions, to which certain speakers fled, rather than dispersion centres.

South America is one of the most linguistically differentiated areas of the world. Various scholars hold the plausible view that all American Indian languages are ultimately related. The great diversification in South America, in comparison with the situation of North America, can be attributed to the greater period of time that has elapsed since the South American groups lost contact among themselves. The narrow bridge that allows access to South America (i.e., the Isthmus of Panama) acted as a filter so that many intermediate links disappeared and many groups entered the southern part of the continent already linguistically differentiated.