A word for “silence” appearing in names like Amon Dîn “Silent Hill, (lit.) *Hill of Silence” (LotR/747; PE17/95) and Taur-na-Chardhîn “Forest of Southern Silence” (WJ/185). As originally conceived, it was probably based on an (unattested) root *√DIN as indicated by ᴹQ. lína- “be silent” from the late 1940s (PE23/76 note #19).

Conceptual Development: Tolkien’s use of this noun and its associated adjective dínen “silent” was inconsistent. The adjective should have been mutated in names like Rath Dínen “Silent Street”, but it remained unchanged (LotR/826). This may reflect Tolkien’s original reluctance to use dh in names while writing The Lord of the Rings. To reconcile these inconsistencies, Tolkien said in his Unfinished Index to The Lord of the Rings that the proper form of these words was tîn and tínen and both of these were adjectives meaning “silent” or “quiet” (RC/551).

Neo-Sindarin: For purposes of Neo-Sindarin, I would stick to noun dîn “silence” and adjective dínen “silent” to avoid conflicts with √TIN “spark”.