The language isolate

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A language for which no relationship to any other language has been demonstrated — which is a statement about the state of the evidence, not about the language. Isolates are not primitive, not unusually old, and not structurally peculiar; Basque is an ordinary language in every respect except that its relatives are gone. That is the usual explanation: an isolate is what remains when every other member of its family has died without record, so isolates should be understood as survivors of extinctions rather than as lineages that never had kin. A second and less common route is documentation failure — a language recorded too thinly for correspondences to be established either way. The status is also revisable in only one direction: a demonstration can convert an isolate into a family member, but no demonstration can prove a language has no relatives, since absence of a proof is not a proof of absence. How many isolates exist depends on the classifier: catalogues that treat each isolate as a family of one report far more families than catalogues that count only multi-member groups, which is one of the two reasons published family counts differ so widely.

A node is not a place. Drawing it on a map would assert something about the world that no stored fact supports.