The Sundering of the Elves

In J. R. R. Tolkien's legendarium, the Elves are a sundered (divided) people. They awoke at Cuiviénen on the continent of Middle-earth (see: Awakening of the Elves), where they were divided into three tribes: Minyar (the Firsts), Tatyar (the Seconds) and Nelyar (the Thirds). After some time, they were summoned by Oromë to live with the Valar in Aman. That summoning and the Great Journey that followed split the Elves into two main groups (and many minor ones), which were never fully reunited.

The name Quendi refers to all elves.

Concept

It has been observed in the Lhammas and other writings like "The Etymologies" that Tolkien employed the Indo-European type of proto-languages with branches and sub-branches of language families while inventing his various languages of Middle-earth. This "concept of increasing separation" is analogous to the Sundering of the Elves

[wikipedia]