A
language isolate, in the absolute sense, is a
natural language with no demonstrable genealogical (or "genetic") relationship with other living languages; that is, one that has not been demonstrated to descend from an ancestor common to any other language. They are in effect
language families consisting of a single language. Commonly cited examples include
Basque,
Ainu,
Burushaski, and
Korean, though in each case a minority of linguists claim to have demonstrated a relationship with another language (see
Dene-Caucasian,
Karasuk, and
Altaic, for example).
With context, a language isolate may be understood to be relatively isolated. For instance, Albanian, Armenian, and Greek are commonly called 'Indo-European isolates'. While part of the Indo-European family, they do not belong to any established branch (like the Romance, Indo-Iranian, Slavic or Germanic branches), but instead form independent branches of their own. However, without such a disambiguating context, "isolate" is understood to be in the absolute sense.
Some languages have become isolates in historical times, after all their known relatives went 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. The opposite also occurs languages once seen as isolates may be reclassified as small families. This happened with Japanese when it was recognized that certain Japanese "dialects", such as Okinawan, were languages in their own right, and the Japonic family was formulated.
Language isolates may be seen as a special case of unclassified languages, languages that remain unclassified even after extensive efforts. If eventually such efforts do prove fruitful, a language previously considered an isolate may no longer be considered one; this has happened with the Yanyuwa language of northern Australia, which has recently been placed in the Pama-Nyungan family. Since linguists do not always agree on whether a genetic relationship has been demonstrated, it is often disputed whether a language constitutes a true isolate or not.
