There are two known dialects of Danian: the Ossiriandic or Ossiriandeb dialect spoken by the Green Elves who entered Beleriand (LR/176, 189), and the Leikvian or East Danian dialect spoken by those Elves who remained beyond the Blue Mountains (LR/196). In the Comparative Tables, Tolkien described Ossiriandic as being of an “Old English type” and East Danian as resembling Old Norse (PE19/22). Whether the two dialects were mutually intelligible is unclear. Most of their phonetic developments were the same (except for vowels), but Tolkien given them two separate columns in the Comparative Tables, which he did not do with the various dialects of Ilkorin or Noldorin.

In The Etymologies, Tolkien marked most words as simply Danian (Dan.), only a few as Ossiriandic (Oss.), and none as East Danian. Based on phonetic evidence, however, many of these “Danian” words were actually Ossiriandic. For example, Dan. snæ̂s had a long [ǣ], which became [ā] in East Danian (PE19/25). Further, Dan. ealc < ᴹ✶alkwā shows evidence of [w] vanishing after medial velars [k], something that only occurred in Ossiriandic (PE19/23). Examples of vowel-breaking such as Dan. beorn and Dan. sc(i)ella more strongly resemble Old English than Old Norse. Finally, the Danian examples used “c” to represent [k] orthographically, which in the Comparative Tables was true of Ossiriandic but not East Danian.

The only attested word that might be from the East Danian dialect is that people’s name for themselves: Leikvir. It shows a [v] after velar [k], and the change [kw] > [kv] is known to have occurred in East Danian (PE19/23).