The Etymologies are not a unified whole, but incorporate layer upon layer of changes. It was not meant to be published. In his introduction to The Etymologies, Christopher Tolkien wrote that his father was "more interested in the processes of change than he was in displaying the structure and use of the languages at any given time." The Etymologies has the form of a scholarly work listing the "bases" or "roots" of the protolanguage of the Elves: Common Eldarin and Primitive Quendian. Under each base, the next level of words are "conjectural", that is, not recorded by Elves or Men but presumed to have existed in the proto-Elvish language. After these, actual words which did exist in the Elvish languages are presented. Words from the following Elvish languages are presented: Danian, Doriathrin, Eldarin, Noldorin, Ilkorin, Lindarin, Old Noldorin, Primitive Quendian, Qenya, Telerin. The following examples from The Etymologies illustrate how Tolkien worked with the "bases":
BAD-*bad- judge. Cf. MBAD-. Not in Q . N bauð judgement; badhor, baðron judge.
TIR-watch, guard. Q tirin I watch, pa.t. tirne; N tiri or tirio, pa.t. tiriant. Q tirion watch-tower, tower. N tirith watch, guard; cf. Minnas-tirith. PQ *khalatirnō 'fish-watcher', N heledirn = kingfisher; Dalath Dirnen 'Guarded Plain'; Palantir 'Far-seer'.
This organization reflects what Tolkien did in his career as a philologist. With English words, he worked backwards from existing words to trace their origins. With Elvish he worked both backward and forward. The etymological development was always in flux but the lexicon of the Elvish tongues remained rather stable. An Elvish word once invented would not change or be deleted but its etymology could be changed many times. Tolkien was much interested in words. Thus The Etymologies are preoccupied with them, only a few Elvish phrases are presented. The Etymologies discuss mainly the Quenya, Old Noldorin, and Noldorin languages. The text give many insights into Elvish personal and place names which otherwise would remain opaque.
Sundokarme: base structure
Christopher Tolkien stated that his father "wrote a good deal on the theory ofsundokarme or 'base structure'... but like everything else it was frequently elaborated and altered".
Addenda and corrigenda
In 2003 and 2004, Vinyar Tengwar issues 45 and 46 provided addenda and corrigenda to the original published text, which has not since been corrected in book form.