Noldorin
gwanw
noun. death (act of dying)
gwanw
noun. death (act of dying, not death as a state or abstract)
gwann
adjective. departed, dead
alf
noun. swan
alf
noun. swan
gwanath
noun. death (act of dying)
guruth
noun. death
guruth
noun. death
gwanath
noun. death (act of dying, not death as a state or abstract)
gûr
noun. death
penedh
noun. Elf
penn
noun. Elf
There were a couple of words for “death” under the root ᴹ√WAN “depart” in The Etymologies of the 1930s: N. gwanath and gwanw, the latter from primitive ᴹ√wanwē (Ety/WAN). Tolkien specified that these words referred to the “act of dying”, as opposed to guru which was “Death as a state or abstract”. These death-words from ᴹ√WAN may originally have been euphemistic, or perhaps they refer to the departure of Elvish spirits to Valinor.
Neo-Sindarin: Most Neo-Sindarin writers adapted N. gwanw as ᴺS. gwanu to better fit Sindarin spelling conventions, as suggested in HSD (HSD). I would use the words gwanath and gwanu only for the death of individuals, and mainly for deaths that are natural or peaceful. For violent deaths I would use gurth instead, and for the state of death or Death as an abstraction I would use guru as noted above.