The Sindar of Beleriand were divided in several groups, and their language had developed some dialects. North Sindarin, the flavour of Sindarin spoken by the Mithrim, the northernmost group of the Sindar, differed from the Sindarin of Beleriand proper in many aspects. It was this language which was adopted by the exiled Noldor after their return to Middle-earth, and by their mortal allies, the House of Beor. During this time North Sindarin was changed much, partially due to the adoption of Quenya features, and partially due to the love of the Noldor for making linguistic changes. Beren's heritage was clear to Thingol of Doriath as he spoke the North Sindarin of his homeland.
North Sindarin retained many features of Archaic Sindarin which had been lost in the Sindarin of Beleriand proper, but also went through several changes of its own: lenition occurred far less in this dialect than in the other dialects.
After the end of the First Age, the survivors of Beleriand's realms generally adopted the more southern variants of Sindarin, but several proper names uninterpretable in normal Sindarin which remained in use during the Third Age show North Sindarin influence.
 Other versions of the legendarium
In Tolkien's earliest writings, there was a language called Ilkorin, the language of the Ilkorindi (the Dark Elves who stayed in the Great Lands). After Tolkien evolved his mythology, the background and setting of the stories changed, and Ilkorin was replaced by Sindarin, the language of the Sindar.
Edward Kloczko observed that the few words mentioned as "Mithrim" fit to the phonological changes and principles seen in Ilkorin: for example Mithrim has ô where Sindarin has au, and retains final -v and -m where Sindarin has final -w; he theorized that Tolkien recycled parts of Ilkorin as Mithrim.
 The case of cw
Ilkorin, which was conceived by Tolkien for an earlier version of the setting, maintains primitive kw, which stays cw or c in some Ilkorin words such as alch (ALÁKwÂ), côm (KwAM), cwess (KwESS), salch (SALÁKwÊ): a phonetic retention that would be unexpected in a Sindarin dialect. (Also, some ancestral sounds extinct in Sindarin were changed into the viable sounds "g" and "go" in Ilkorin.)
Assuming North Sindarin is not, linguistically speaking, completely identical to Ilkorin, and thus as in other Sindarin dialects the "kw" sound was not conserved, the aforementioned words may exist in the forms of *alph, *pôm, *pess, *salph in North Sindarin.
 Mithrimin and Doriathrin
The word lómin (cf. Dor-Lómin) was a variant of lómen "echoing", both in Doriathrin, another dialect of Tolkien's early legendarium; Doriathrin shows adjectives ending in -in instead of standard Sindarin -en (Dungorthin, muilin).
- ↑ J.R.R. Tolkien, "Words, Phrases and Passages in Various Tongues in The Lord of the Rings", in Parma Eldalamberon XVII (edited by Christopher Gilson) p.134
- ↑ J.R.R. Tolkien, Christopher Tolkien (ed.), The War of the Jewels, "Index"
- ↑ Edward Kloczko, "Ilkorin and North Sindarin", in Tyalië Tyelelliéva #9, October 1996
- ↑ J.R.R. Tolkien, Christopher Tolkien (ed.), The Lost Road and Other Writings, "Part Three: The Etymologies", entry LAM
- ↑ J.R.R. Tolkien, "Words, Phrases and Passages in Various Tongues in The Lord of the Rings", in Parma Eldalamberon XVII (edited by Christopher Gilson) p.133
- J.R.R. Tolkien, Christopher Tolkien (ed.), The War of the Jewels
- Ryszard Derdzinski, "Northern Dialect of Sindarin", Gwaith-i-Phethdain
- Helge Fauskanger, "Ilkorin", Ardalambion
- Roman Rausch, "Mithrimin", at Sindanórië
- Wordlist of Mithrim, comprised of Ilkorin corpus with neo-North Sindarin "updates"
|Languages in Tolkien's works|
|Elvish languages||Avarin · Common Eldarin · Gnomish · Nandorin · Noldorin · Primitive Quendian · Quenya (Exilic · Qenya · Telerin · Valinorean · Vanyarin) · Silvan · Sindarin (Doriathrin · Falathrin · Númenórean · Ilkorin · Mithrim · Old)|
|Mannish languages||Adûnaic · Dalish · Drúedainic · Dunlendish · Pre-Númenórean · Rohirric · Taliska · Westron (Hobbitish)|
|Dwarvish languages||Iglishmêk · Khuzdul|
|Other languages||Black Speech · Entish · Orkish · Valarin · Warg-language|
|Outside the legendarium||Animalic · Arktik · Mágol · Naffarin · Nevbosh|
|Scripts||Angerthas/Cirth (Daeron · Erebor · Moria) · Goblin Alphabet · Moon-letters · Tengwar · Sarati · Valmaric script|
|"A Secret Vice" (book) · "The Lhammas" · "The Tree of Tongues" · Sub-creation|