A language isolate is a natural language with no demonstrable genetic relationship with other living languages. Examples include Basque, Ainu, Burushaski, and Japanese.
Some languages became isolates in historical times, after all their known relatives became extinct. The Pirahã language of Brazil is one such example, the last surviving member of the Mura family. Others, like Basque, have been isolates for as long as their existence has been documented.
Genetic relationship
The term "genetic relationship" above is meant in the sense of historical linguistics. Almost all languages spoken in the world today can be grouped by this criterion into a relatively small number of families. Thus English is clearly related to several other Indo-European languages, and Mandarin to many other Sino-Tibetan languages. Language isolates are few and scattered and as such, tends to increase the amount of work that is done on them.
Looking for relationship
There is some possiblity that all languages spoken in the world today are genetically related, by descent from a single ancestral tongue; the established language families would then be only the upper branches of the genealogical tree of all languages. For this reason, isolate languages have been the object of uncountable studies seeking to uncover their genealogy. Thus, for instance, Basque has been compared with every living and extinct language family, from Sumerian to the South Caucasian — without convincing results.
Isolate, not Isolated
One should not confuse the concept of a language isolate with a language whose speakers are isolated in some sense, e.g. because they have little contact with other cultures (like the language of Easter Island), or because they live far away from the regions where related languages are spoken (like the Malagasy language of Madagascar, whose closest relatives are spoken in Southeast Asia). These two languages are definitely not isolates.
List of language isolates
Below is a list of known language isolates, along with notes on possible relations to other languages or language families:
| Language | Comments |
| Ainu | Endangered language. |
| Basque | No known living relatives. Aquitanian is commonly regarded as a director ancestor of Basque. Some linguists have claimed similarities with various languages of the Caucasus, especially because of its ergative case system, but the resemblances seem superficial. Other linguists have proposed a relation to Iberic. |
| Burushaski | Little information available. |
| Etruscan | Not well understood at present |
| Nivkh | or Gilyak. A Palaeosiberian language spoken in the lower Amur River basin and on the Sakhalin Islands; Ainu is also spoken on Sakhalin. |
| Iberic | There are lexical coincidences with Basque, but it is hard to know if they are more than a result of vicinity. |
| Japanese | Possibly related to Korean language, though not yet proven. Connections to the Altaic languages have also been proposed. |
| Ket | No known relatives. Some linguists have attempted to show a relationship with Burushaski. |
| Korean | Possibly related to Japanese language, though not yet proven. Connections to the Altaic languages have also been proposed. |
| Nahali | |
| Taiap | |
| Sumerian |