An areal feature, in linguistics, is the appearance of a given feature of typology in several unrelated languages due to the influence of geographical closeness.
While most features of a language can be genetically traced back to an ancestor language (an earlier stage of development), areal features are the result of horizontal "contagion" from neighbouring populations of genetically unrelated languages. For linguists researching a large geographic area, it may be sometimes difficult to attribute certain features to areal influence instead of relatedness.
Among other examples, the prevalence of contrasting tone among East Asian languages is believed to be an areal feature. Another example is the occurrence of click consonants in several South African languages; they are believed to have originated in the Khoisan phylum, but are now also part of the phoneme inventory of the Bantu Nguni languages Zulu and Xhosa.
