Sindarin is Tolkien’s Elvish language that means “Grey-elvish.”
Tolkien created Sindarin as a language associated especially with the Sindar, or Grey Elves. It is one of the best-developed languages in his legendarium and is used by many Elves in the stories of the First, Second, and Third Ages.
The language’s historical structure was influenced by Tolkien’s study of real languages, particularly Welsh. Sindarin and Quenya are related within Tolkien’s fictional history, but they have different sound patterns, vocabularies, and social associations. Sindarin became more widely used in Middle-earth than Quenya during the later ages.
Quenya is often confused with Sindarin because both are Elvish languages created by Tolkien. Quenya is associated with the High Elves and has strong Finnish and Latin influences. Khuzdul is the secret language of the Dwarves, while Adûnaic was spoken by the people of Númenor.