Language family

A language family is a group of languages related through descent from a common ancestor, called the proto-language of that family. The term family is a metaphor borrowed from biology, with the tree model used in historical linguistics analogous to a family tree, or to phylogenetic trees of taxa used in evolutionary taxonomy. Linguists thus describe the daughter languages within a language family as being genetically related. The divergence of a proto-language into daughter languages typically occurs through geographical separation, with different regional dialects of the proto-language undergoing different language changes and thus becoming distinct languages over time.

One well-known example of a language family is the Romance languages, including Spanish, French, Italian, Portuguese, Romanian, Catalan, Romansh, and many others, all of which are descended from Vulgar Latin. The Romance family itself is part of the larger Indo-European family, which includes many other languages native to Europe and South Asia, all believed to have descended from a common ancestor known as Proto-Indo-European.

A language family is usually said to contain at least two languages, although language isolates — languages that are not related to any other language — are occasionally referred to as families that contain one language. Conversely, there is no upper bound to the number of languages a family can contain. Some families, such as the Austronesian languages, contain over 1,000.

Language families can be identified from characteristics shared amongst their languages. Sound changes are one of the strongest pieces of evidence that can be used to identify a genetic relationship because of their predictable and consistent nature, and through the comparative method can be used to reconstruct proto-languages. However, languages can also change through language contact, which can falsely suggest genetic relationships. For example, the Mongolic, Tungusic, and Turkic languages share many similarities that have led several scholars to believe they were related. These supposed relationships were later discovered (in the view of most scholars) to be derived through language contact and thus they are not related through shared ancestry. Eventually though, intense language contact with other language families, and inconsistent changes within the original language family, will obscure inherited characteristics and make it virtually impossible to deduce earlier relationships; even the oldest demonstrable language family, Afroasiatic, is far younger than language itself.

Estimates of the number of language families in the world may vary widely. According to Ethnologue there are 7,151 living human languages across 142 different language families. Lyle Campbell (2019) identifies a total of 406 independent language families, including isolates.

Ethnologue 27 (2024) lists the following families that contain at least 1% of the 7,164 known languages in the world; while Glottolog 5.0 (2024) lists the following as the largest families, of 7,788 languages (other than sign languages, pidgins, and unclassifiable languages):

Language counts can vary significantly depending on what is considered merely a dialect; for example Lyle Campbell counts only 27 Otomanguean languages, although he, Ethnologue and Glottolog also disagree as to which languages belong in the family.

Neither Ethnologue nor Glottolog list the language families of sign languages. Of sign language families, the Francosign family, hosting around 70 languages, is by far the largest and most widespread.