yá (2) conj. “when” in the sentence yá hrívë tenë, ringa ná “when winter comes, it is cold” (VT49:23). Compare írë #2.
ya (1) relative pronoun "which, what" (attested in VT43:28, 34 and in the Arctic sentence), with locative suffix in Namárië: see #yassë. According to VT47:21, ya is impersonal, "which" rather than "who(m)" (compare the personal form ye). The dative form yan (q.v.) is however used for "to whom" (rather than “to which”) in one text, indicating that Tolkien did not always distinguish between personal and impersonal forms. In the phrase lúmessë ya [variant: yá] firuvammë, *"in [the] hour that we shall die", the relative pronoun is not explicitly marked for case and is evidently understood to share the case of the preceding noun (hence not *lúmessë yassë... "in [the] hour in which"...) (VT43:27-28) Presumably, ya has the plural form *yar (e.g. *i nati yar hirnen “the things that/which I found”).
