Altaic languages
There is ongoing debate about whether the Turkic family is itself a branch of a larger Altaic family, including Japanese, Korean, Mongolian and Tungusic. The nineteenth-century Ural-Altaic theory, which grouped Turkish with Finnish, Hungarian and Altaic languages, is controversial. The theory was based mostly on the fact these languages share three features: agglutination, vowel harmony and lack of grammatical gender.