315. The uses of the subjunctive and optative in independent clauses have been shown to fall in each case into two main groups. In one set of meanings the mood expresses desire on the part of the speaker; to this belong the Subjunctive of Command and Prohibition, and the Optative of wish. In the other the mood is a kind of future; the subjunctive being an emphatic or confident future (like οur future with shall), the optative a softened future, expressing expectation, or mere admission of possibility (the English may or should).
These two sets of meanings may be called the "quasi-imperative," and the "quasi-future." We must remember however that they are not always clearly separable, but are connected by transitional or intermediate uses: such as (e.g.) the subjunctive which expresses necessity (§ 277), and the optative of concession (§ 299.d).