574. The subjunctive, as has been pointed out, becomes nearly extinct at an early period in the history of the language; there are left of it in classical usage only two relics: the use of its first persons in an imperative sense, or to signify a necessity or obligation resting on the speaker, or a peremptory intention on his part; and the use of unaugmented forms (579), with the negative particle मा mā́, in a prohibitive or negative imperative sense.
a. And the general value of the subjunctive from the beginning was what these relics would seem to indicate; its fundamental meaning is perhaps that of requisition, less peremptory than the imperative, more so than the optative. But this meaning is liable to the same modifications and transitions with that of the optative; and subjunctive and optative run closely parallel with one another in the oldest language in their use in independent clauses, and are hardly distinguishable in dependent. And instead of their being (as in Greek) both maintained in use, and endowed with nicer and more distinctive values, the subjunctive gradually disappears, and the optative assumes alone the offices formerly shared by both.
575. The difference, then, between imperative and subjunctive and optative, in their fundamental and most characteristic uses, is one of degree: command, requisition, wish; and no sharp line of division exists between them; they are more or less exchangeable with one another, and combinable in coördinate clauses.
a. Thus, in AV., we have in impv.: çatáṁ jīva çarádaḥ do thou live a hundred autumns; ubhāú tāú jīvatāṁ jarádaṣṭī let them both live to attain old age; — in subj., adyá jīvāni let me live this day; çatáṁ jīvāti çarádaḥ he shall live a hundred autumns; — in opt., jī́vema çarádāṁ çatā́ni may we live hundreds of autumns; sárvam ā́yur jīvyāsam (prec.) I would fain live out my whole term of life. Here the modes would be interchangeable with a hardly perceptible change of meaning.
b. Examples, again, of different modes in coördinate construction are: iyám agne nā́rī pátiṁ videṣṭa ... súvānā putrā́n máhiṣī bhavāti gatvā́ pátiṁ subhágā ví rājatu (AV.) may this woman, O Agni! find a spouse; giving birth to sons she shall become a chieftainess; having attained a spouse let her rule in happiness; gopāyá naḥ svastáye prabúdhe naḥ púnar dadaḥ (TS.) watch over us for