Unclassified languages are languages whose genetic affiliation has not been established by means of historical linguistics. If this state of affairs continues after significant study of the language and efforts to relate it to other languages, as in the case of Basque, it is termed a language isolate; an unclassified language is therefore one which may belong to an established family once better data or research is available. Languages can be unclassified for a variety of reasons, mostly due to a lack of reliable data but sometimes due to the confounding influence of language contact. Some poorly known extinct languages, such as Gutian, are simply unclassifiable.