Union-vowels. All the simple vowels come to assume in certain cases the aspect of union-vowels, or insertions between root or stem and ending of inflection or of derivation.

a. That character belongs oftenest to i, which is very widely used: 1. before the s of aorist and future and desiderative stems, as in ájīviṣam, jīviṣyā́mi, jíjīviṣāmi; 2. in tense-inflection, especially perfect, as jijīvimá; occasionally also present, as ániti, róditi; 3. in derivation, as jīvitá, khánitum, janitṛ́, rociṣṇú, etc. etc.

b. Long ī is used sometimes instead of short: thus, ágrahīṣam, grahīṣyā́mi; bravīti, vāvadīti; tarītṛ́, savītṛ́; it is also often introduced before s and t of the 2d and 3d sing. of verbs: thus, ā́sīs, ā́sīt.

c. For details respecting these, and the more irregular and sporadic occurrences of u- and a-vowels in the same character, see below.