In linguistics, a superfamily (or macrofamily) is a phyletic unit encompassing several language families. The term is generally used for conjectural families, e.g. the Nostratic, Dene-Caucasian, Altaic, and Proto-World groupings. The term is typically invoked to describe theoretical associations between established language families (e.g. between Turkic, Mongolian, and Tungusic languages, in the case of Altaic), and has come to carry a connotation of hypothesis, and therefore, controversy. As such, it is rarely applied to accepted groupings like the Indo-European language family. Broadly conceived, linguistics is the scientific study of human language, and a linguist is someone who engages in this study. ... Most languages are known to belong to language families (families hereforth). ... Nostratic is a highly controversial language super-family that putatively links many Eurasian language families. ... The Dene-Caucasian (or Sino-Caucasian) language family is a conjectural macrofamily containing the Sino-Tibetan, North Caucasian, Yeniseian and Na-Dene languages. ... Altaic is a language family which includes 60 languages spoken by about 250 million people, mostly in and around Central Asia and Far East. ... The term Proto-World language refers to the hypothetical latest common ancestor of all the worlds languages, an ancient language from which all modern languages and language families – and usually including all known dead languages – derive. ... The Turkic languages are a group of closely related languages that are spoken by a variety of people distributed across a vast area from Eastern Europe to Siberia and Western China. ... Tungusic languages (or Manchu-Tungus languages) are spoken in Eastern Siberia and Manchuria. ... A hypothesis (= assumption in ancient Greek) is a proposed explanation for a phenomenon. ... The Indo-European languages include some 443 (SIL estimate) languages and dialects spoken by about three billion people, including most of the major language families of Europe and western Asia, which belong to a single superfamily. ...