An optative is the expression of a wish, and Quenya usually formulates such expressions using the adverb nai “may it be that, be it that, maybe”. Its most famous use is in nai hiruvalye Valimar, nai elye hiruva “maybe thou shalt find Valimar, maybe even thou shalt find it” in the Namárië poem (LotR/378). Tolkien described this formulation in several places:

Quenya expression of wish. nai + future. nai elye hiruva. but God bless you (which includes now), nai + present indicative. nai Eru tye mānata (1967 linguistic notes, PE17/75).

The last lines of the chant express a wish (or a hope) that though she could not go, Frodo might perhaps be allowed to do so. Nā-i > nai “be it that” expresses rather a wish than a hope, and would be more closely rendered “may it be that” (thou wilt find) than by “maybe” (Commentary on Namárië, 1967, The Road Goes Ever On, RGEO/60).

Nai: “be it that, may it be that” Nai tiruvantes: “be it that they will guard it”, i.e. “may they guard it” (UT/217).

“can” [=] have opportunity, chance, or permission - be allowed by circumstances, 'way of the world;. √NAYA. Hence nai (> nayi) “it may be, there is a chance or possibility”, maybe. This mostly used where the opportunity or permission is certain or very probable (“may well be”). It is not used personally but either with dative pronoun or with an undefined clause (in which case nai is virtually adverbial in our syntax). nai nin híres “it may well chance for me to find it” or nai hirinyes. In this case the verb may be future [and] usually is (nai hirinyes being used rather in general statements, I have chances of finding it, almost equivalent to our “I sometimes find it”) (Late Notes on Verb Structure, LVS, 1969, PE22/151).

Most of the glosses in these notes represent the meaning of nai as “be it that”, consistent with the etymology given in RGEO = nā + i = “(imperative) be [it] that”. In LVS, Tolkien considered another possibility, that nai was an expression of possibility, from an impersonal verb nai “it may be, there is a possibility [that]”, but functioning adverbially when combined with the future. I think this etymology in LVS is problematic (elsewhere √NAY = “cause bitter grief or pain” as in nainie “lament”), so I prefer the nā + i derivation.

Carl Hostetter analyzed several nai expressions from the late 1960s in his article Five Late Quenya Volitive Inscriptions (VT49/38-48):

• nai elen siluva parma-restalyanna meldonya “*may a star shine upon your book-fair, my friend” (VT49/38).
• nai elen siluva lyenna “*may a star shine upon you” (VT49/40).
• nai amanya onnalya ter coivierya “*may your child be blessed throughout his/her life” (VT49/41).
• nai elen atta siluvat aurenna veryanwesto “*may two stars shine upon the day of your wedding” (VT49/44).
• nai laure lantuva parmastanna lúmissen tengwiesto “may (a) golden light fall on your book at the times of your reading” (VT49/47).

Most of these follow the same formula of nai + future, but the third phrase nai amanya onnalya ter coivierya has no explicit verb. As suggested by Hostetter, it seems to have an implied (aorist?) “to be”, with ná “to be” omitted as it often the case in Quenya. Tolkien wrote a note below this phrase that states “nai ‘imper[ative]’ of wishes precedes adj”, which further supports the idea that this is a predicate expression. This phrase, along with nai Eru tye mánata “God bless you” given above (PE17/75), indicate nai can be used with wishes that include the present time, such as for blessings.

There are several “near optatives” in the Átaremma prayer from the 1950s (VT43/12):

• na aire esselya “hallowed be thy name”.
• aranielya na tuluva “thy kingdom come”.
• na care indómelya “thy will be done”.

These examples skirt the boundary between a genuine optative with nai and an indirect imperative with the verb “be”. In earlier versions of the prayer some of these phrases were explicitly imperative:

• á tula túrinastalya or túrindielya á tuluva “thy kingdom come” (VT43/10-11).
• á cara mendelya “thy will be done” (VT43/11).

These “imperatives” are already unusual in that they use verb tenses other than the aorist. Perhaps there is a spectrum of more forceful to less forceful “wishes” here:

• á tule aranielya “let your kingdom come” (imperative).
• na tule aranielya “your kingdom come” (intermediate).
• nai aranielya tule “may your kingdom come” (optative).

Conceptual Development: The use of nai with optatives dates all the way back to the Early Qenya Grammar (EQG), but with a slightly different origin:

The conditional or subjunctive. This is not expressed inflectionally but by particles, nai and ki, of which nai represents remoter possibility (“might”), ki (nearer) “may”. The pure optative is also often expressed by nai, or {naiki >>} naike combined, at head of wish ... naike hi·tule “would she might come” (of something remotely possible, or impossible) (PE14/59).

In EQG nai is an expression of possibility, much as it was four decades later in LVS, though in EQG it was a particle rather than an impersonal verb.