Sindarin is the Elvish language spoken by many Grey-elves in J.R.R. Tolkien’s legendarium.
Tolkien based Sindarin primarily on the sound and historical development of Welsh, one of the languages he admired as a philologist. In the fictional history of Middle-earth, Sindarin developed among the Sindar, or Grey-elves, who remained in Beleriand during the First Age. It became a major spoken Elvish language in Middle-earth.
Quenya is the main language of the High Elves and is more closely associated with the Ñoldor and formal or literary use. This distinction is a common source of confusion because Tolkien’s Elvish languages share vocabulary and appear together in names and poetry.
Sindarin appears in names such as Mithrandir, meaning “Grey Pilgrim,” and Galadriel. Tolkien created extensive grammar and vocabulary for it, although the surviving material is not a complete language in the same way as a modern natural language.