1. While IE II had possibly only Indicative and Imperative, a Subjunctive and an Optative were added in the third stage, both used in the four Tenses. Not all IE III dialects, however, developed the system with a subjunctive and an optative.
2. The Imperative is usually formed with a pure stem, adding sometimes adverbial or pronominal elements.
2. Some common Subjunctive marks are the stem endings -a, -e, and -s, but it is more usually formed with the opposition athematic / thematic or thematic / thematic-long vowel for Indicative/Subjunctive pairs.
NOTE. There were, however, no stems reserved for the Subjunctive, as the systematizations that are known to us happened after the great migrations, and until that time no general subjunctive mark existed. In some dialects the subjunctive was not systematized at all, as in Baltoslavic, but for the sake of unity a system has to be developed.
3. The Optative is different from the Subjunctive in that it has its own characteristic suffix, reserved for it: -ie / -i; in thematic Tenses it is -oi, which is the same suffix added to the theme vowel.
4. The Moods are used as follows:
a. The Indicative Mood is used for most direct assertions and interrogations.
b. The Subjunctive Mood has many idiomatic uses, as in commands, conditions, and various dependent clauses. It is often translated by the English Indicative; frequently by means of the auxiliaries may, might, would, should; sometimes by the (rare) Subjunctive; sometimes by the Infinitive; and often by the Imperative, especially in prohibitions.
c. The Imperative is used for exhortation, entreaty, or command; but the Subjunctive could be used instead:
d. The Infinitive is used chiefly as an indeclinable noun, as the subject or complement of another verb. In special constructions it takes the place of the Indicative, and may be translated by that mood in English.