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Na-Dene ( //; also Nadene, Na-Dené, Athabaskan–Eyak–Tlingit, Tlina–Dene) is a family of Native American languages that includes at least the Athabaskan languages, Eyak, and Tlingit languages. An old inclusion of Haida is now considered doubtful.
In February 2008, a proposal connecting Na-Dene (excluding Haida) to the Yeniseian languages of central Siberia into a Dené–Yeniseian family was published and well-received by a number of linguists.  It was proposed in a 2014 paper that the Na-Dene languages of North America and the Yeniseian languages of Siberia had a common origin in a language spoken in Beringia, between the two continents. 
Edward Sapir originally constructed the term Na-Dene to refer to a combined family of Athabaskan, Tlingit, and Haida (the existence of the Eyak language was not known to him at the time). In his "The Na-Dene languages: A preliminary report", he describes how he arrived at the term (Sapir 1915, p. 558):
The name that I have chosen for the stock, Na-dene, may be justified by reference to no. 51 of the comparative vocabulary. Dene, in various dialectic forms, is a wide-spread Athabaskan term for "person, people"; the element *-ne (*-n, *-η) which forms part of it is an old stem for "person, people" which, as suffix or prefix, is frequently used in Athabaskan in that sense. It is cognate with H. na "to dwell; house" and Tl. na "people". The compound term Na-dene thus designates by means of native stems the speakers of the three languages concerned, besides continuing the use of the old term Dene for the Athabaskan branch of the stock.
In its non-controversial core, Na-Dene consists of two branches, Tlingit and Athabaskan–Eyak:
- Tlingit: 700 speakers ( Michael Krauss, 1995)
For linguists who follow Edward Sapir in connecting Haida to the above languages, Haida represents an additional branch, with Athabaskan–Eyak–Tlingit together forming the other. Dene or Dine (the Athabaskan languages) is a widely distributed group of Native languages spoken by associated peoples in Alberta, British Columbia, Manitoba, Northwest Territories, Nunavut, Saskatchewan, Yukon, Alaska, parts of Oregon, northern California, and the American Southwest as far as northern Mexico.
The southwestern division of Athabaskan is also called Southern Athabaskan or Apachean, and includes Navajo and all the Apache dialects. Eyak was spoken in south-central Alaska; the last speaker died in 2008. Navajo is by far the most widely spoken language of the Na-Dene family, spoken in Arizona, New Mexico, and other regions of the American Southwest.
All of these languages share a highly complex prefixing verb structure in which tense and mood markers are interdigitated between subject and object agreement markers. The morphological hallmark of the family is a series of prefixes found directly before the verb root that raise or lower the transitivity of the verb word. These prefixes, traditionally known as "classifiers", derive historically from a combination of three distinct classes of morphemes and are not found in any other Native American language family.
The phoneme system contains a large number of dorsal (velar or uvular) consonants (fronting in many modern Athabaskan languages to palatals and velars, correspondingly) as well as a general absence of labial obstruents (except where /b/ has arisen from *w). In the historical phonology there is a widespread tendency, observable across many Athabaskan languages, for phonemic tonal distinctions to arise from glottal features originally found at the end of the syllable. The glottal features in question are often evident in Eyak or Tlingit. These languages are typologically unusual in containing extensive prefixation yet being SOV and postpositional, features normally associated with suffixing languages.
A genealogical connection between the Tlingit, Eyak and Athabaskan languages was suggested early in the 19th century, but not universally accepted until much later. Haida, with 15 fluent speakers (M. Krauss, 1995), was originally linked to Tlingit by Franz Boas in 1894. Both Haida and Tlingit were then connected to Athabaskan by Edward Sapir in 1915. Linguists such as Lyle Campbell (1997) today consider the evidence inconclusive. They have classified Haida as a language isolate. In order to emphasise the exclusion of Haida, Campbell refers to the language family as Athabaskan–Eyak–Tlingit rather than Na-Dene. In 2010 Jeff Leer published extensive primary materials on what he calls PAET (Proto-Athabascan–Eyak–Tlingit).
In 2008, Edward Vajda of Western Washington University presented evidence suggesting that the Na-Dene languages (Athabaskan–Eyak–Tlingit) might be related to the Yeniseian (or Yeniseic) languages of Siberia,  the only living representative of which is the Ket language.
Key evidence by current comparative methodologies includes homologies in verb prefixes and also a systematic correspondence between the distribution of Ket tones and consonant articulations found in Athabaskan–Eyak–Tlingit. Vajda's paper has been favorably reviewed by several experts on Na-Dene and Yeniseic languages, including Michael Krauss, Jeff Leer, James Kari, and Heinrich Werner, as well as a number of other well-known linguists, including Bernard Comrie, Johanna Nichols, Victor Golla, Michael Fortescue, and Eric Hamp. The conclusion of this seminar was that the comparison with Yeniseic data shows that Haida cannot be classified in a genealogical unit with Athabaskan–Eyak–Tlingit. 
According to Joseph Greenberg's controversial classification of the languages of Native North America, Na-Dené (including Haida) is one of the three main groups of Native languages spoken in the Americas. Contemporary supporters of Greenberg's theory, such as Merritt Ruhlen, have suggested that the Na-Dené language family represents a distinct migration of people from Asia into the New World that occurred six to eight thousand years ago, placing it around four thousand years later than the previous migration into the Americas by Amerind speakers; this remains an unproven hypothesis.  Ruhlen speculates that the Na-Dené speakers may have arrived in boats, initially settling near the Haida Gwaii, now in British Columbia, Canada. 
Linguist Edward Sapir suggested that the Sino-Tibetan languages are related to Na-Dené.  More recent hypotheses, e.g. by Sergei Starostin, suggest that Na-Dené (including Haida) may belong to the much broader Dené–Caucasian superfamily, which also contains the North Caucasian languages, Sino-Tibetan languages, and Yeniseian languages.
|tʃʼ||sʼ, tʃʼ (tsʼ)||tɬʼ|
|tsʼ||tsʼ||sʼ, tsʼ||tɬʼ, ɬ|
|ɡʷ||ɖʐ||ɡʷ → ɡ|
|kʷ||ʈʂ||kʷ → k|
|kʷʼ||ʈʂʼ||kʼʷ → kʼ|
|xʷ||ʂ~ʐ||xʷ → x|
|ɢʷ||ɢʷ → ɢ|
|qʷ||qʷ → q|
|qʷʼ||qʷʼ → qʼ||χʼ, qʼ(ʷ)|
|χʷ||χʷ → χ~ʁ||χʷ|
|Extrasystematic fricative correspondences|
|$||x(ʷ) ?||$ (ʃ~xʲ)||xʷ → x; s||χ|
- PAET, PAE and PA stand for Proto-Athabaskan–Eyak–Tlingit, Proto-Athabaskan–Eyak and Proto-Athabaskan, respectively.
- To prevent cluttering the table, phonemes in the PAET, PAE and PA columns are not asterisked.
- Leer (2008, 2010) doesn't reconstruct the PAET affricates */dɮ/, */tɬ/ and */dz/. Judging from their rarity, he assumes they may be attributable to the resolution of former consonant clusters.
- In Athabaskan and Eyak, sibilants can be diminutive variants of shibilants. In Tlingit, on the other hand, shibilants might sometimes be diminutive variants of sibilants. These correspondences are in parentheses.
- Hammarström, Harald; Forkel, Robert; Haspelmath, Martin, eds. (2017). "Athabaskan–Eyak–Tlingit". Glottolog 3.0. Jena, Germany: Max Planck Institute for the Science of Human History.
- Dene–Yeniseic Symposium, University of Alaska Fairbanks, February 2008, accessed 30 Mar 2010
- Mark A. Sicoli and Gary Holton, Linguistic Phylogenies Support Back-Migration from Beringia to Asia, PLoS ONE, March 12, 2014, accessed November 25, 2014.
- See Vajda 2010
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