J.R.R. Tolkien based much of Sindarin’s phonology on Welsh. Sindarin is one of the principal Elvish languages in Tolkien’s legendarium and is associated especially with the Sindar, or Grey Elves.
Tolkien was a professional philologist who designed languages with historical relationships, sound patterns, and changes over time. Sindarin developed from earlier forms in his fictional linguistic history, including Common Telerin and Old Sindarin. Its sounds and appearance were shaped by Tolkien’s interest in Welsh, while its grammar and vocabulary remained part of his own invented system.
Quenya is another major Elvish language, but Tolkien associated its sound and structure more strongly with Finnish and Latin influences. Sindarin should also not be confused with Black Speech, created for Mordor, or Adûnaic, the language of Númenor. Tolkien’s languages were not merely word lists: he created connected families and imagined their speakers’ histories.