Tangkhul is not close to other Naga languages. It is a dialect continuum, in which speakers from neighboring villages may be able to understand each other, but a dialect farther north or south will be less easily understood, if at all. The lingua franca is the Hunphun (Ukhrul) dialect.
The language dialect spoken by the people of Hunphun (the traditional name of Ukhrul) became the most common dialect among the Tangkhuls because the British set up their administration in Ukhrul. The American Baptist missionary Rev. William Pettigrew translated the Bible into the Hunphun dialect.