The Elvish language J.R.R. Tolkien created and developed most extensively was Quenya.
Quenya is one of Tolkien’s constructed languages and is associated particularly with the High Elves. Tolkien based much of its sound and structure on languages he studied, especially Finnish, while also giving it its own vocabulary, grammar, and history within the fictional world.
Sindarin is another major Elvish language and is more commonly spoken by many Elves in Middle-earth during the period of The Lord of the Rings. This distinction causes frequent confusion: Quenya is often treated as a ceremonial or scholarly language in the later histories, while Sindarin is the everyday language of many communities.
Tolkien’s language invention preceded and influenced his storytelling. He built peoples, migrations, and historical relationships partly to provide settings in which his languages could exist. Quenya therefore belongs to both his literary mythology and his lifelong interest in philology.