optative

IPA: ˈɑptʌtɪv

(grammar) A mood of verbs found in some languages (e.g. Sanskrit, Old Prussian, and Ancient Greek, but not English), used to express a wish.
(grammar) A verb or expression in the optative mood.

Examples of "optative" in Sentences

Greek has a particular mood called the optative mood.
Thus the importance to it of the subjunctive or optative mood.
Likewise *-i is absent in all other irrealis moods ie. the optative, and likely too, the subjunctive.
Imperative (prejective), conjunctive or optative (subjective), preterite or perfect (trajective), neutral indicative (objective) are grammatical necessities arising out of times and spaces.
So presumably if *h₁i-yéh₁-n̥t 'they should go' is the optative of an objective verb like *h₁y-énti 'they go', then theoretically *ḱéi-ih₁-th₂e 'you should lie down' rather than later *ḱéi-ih₁-s would have originally been the optative of *ḱéi-th₂or 'you lie down'.
First of all, the 1ps subjunctive is typically understood to simply be *(-o)-oh₂ (although Jasanoff convincingly argues for a purely "athematic"1 *-oh₂ in the earliest stage of PIE, contrasting with present indicative *-mi) and the 1ps optative is normally *-yeh₁m.
However, when developing his general theory of speech acts, Austin abandoned the constative/performative distinction, the reason being that it is not so clear in what sense something is done e.g. by means of an optative utterance, expressing a wish, whereas nothing is done by means of an assertoric one.