The fictional Elvish language J.R.R. Tolkien developed most fully is Quenya.
Quenya is one of Tolkien’s most extensively constructed languages. He modeled parts of its sound and structure on Finnish, Latin, and Greek, while giving it its own grammar, vocabulary, and history. In Tolkien’s mythology, Quenya began as the language of the Elves associated with Valinor and later became a language of lore and ceremony in Middle-earth.
The language appears in names, poems, inscriptions, and formal speech. The opening of Galadriel’s lament, “Namárië,” is one of the best-known substantial Quenya passages in The Lord of the Rings. Tolkien did not treat Quenya as a collection of random fantasy words; he developed historical relationships between it and other Elvish languages.
Sindarin is a different Elvish language and is generally more common in spoken scenes of The Lord of the Rings. Confusing Quenya with Sindarin is one of the most frequent mistakes in discussions of Tolkien’s languages.