Sindarin is the language J.R.R. Tolkien created as the main language of the Sindar Elves.
Within Tolkien’s legendarium, Sindarin developed from the older language of the Elves who remained in Middle-earth. It became the most widely spoken Elvish language among many peoples of Middle-earth during the later histories described in The Lord of the Rings.
Tolkien designed Sindarin as part of a related family of invented languages rather than as an isolated vocabulary list. Its sound patterns and historical development were influenced especially by Welsh, while Quenya, another major Elvish language, was influenced strongly by Finnish and Latin. These linguistic relationships give Tolkien’s fictional cultures a sense of historical depth.
Sindarin and Quenya are often confused because both are Elvish languages and both appear in Tolkien’s writings. Quenya is associated particularly with the High Elves and has a more formal or ancient role in many contexts. Sindarin is the correct answer for the language of the Sindar.