The Elvish language most commonly associated with the Elves of Beleriand is Sindarin.
Sindarin is one of Tolkien’s most developed Elvish languages. In the First Age, it is associated especially with the Sindar, or Grey Elves, of Beleriand. Tolkien based much of its sound and historical development on Welsh, while Quenya draws more strongly on Finnish and other linguistic influences.
Sindarin remains important in later ages because it becomes the everyday Elvish language of many Elves in Middle-earth. Names such as Lothlórien, Minas Tirith, and Mithrandir come from Tolkien’s invented linguistic systems, although not every Elvish-looking name belongs to Sindarin.
Quenya is the major High-elven language and is associated with the Noldor and other learned or ceremonial contexts. The two languages are related within Tolkien’s imagined history but are not interchangeable. Tolkien developed sound changes, vocabulary, and grammar for both, rather than treating them as simple lists of translated names.