Quenya 

oialëa

eternal

oialëa adj. "eternal" (PE17:59)

oialëa

adjective. eternal

Elements

WordGloss
oialë“forever; everlastingly, eternally, in eternity, forever; everlastingly, eternally, in eternity; [ᴹQ.] everlasting age”
-a“adjectival suffix”

oira

eternal

oira adj. "eternal" (OY)

aira

eternal

[aira (4) adj. "eternal" (EY, VT45:13). Changed by Tolkien to oira.]

íra

eternal

[íra adj. "eternal" (GEY, VT45:13; changed by Tolkien to oira, see OY)]

írë

eternal

[írë] (3) noun "eternal" (read "eternity", as suggested by Christopher Tolkien, but the word was in any case changed to oirë)(GEY, VT45:13)