185. But the same change occurs also

But the same change occurs also, on a considerable scale, in external combination, especially in composition. Thus:

a. Both in verbal forms and in derivatives, the final i or u of a preposition or other like prefix ordinarily lingualizes the initial s of the root to which it is prefixed; since such combinations are both of great frequency and of peculiar intimacy, analogous with those of root or stem and affix: thus, abhiṣā́c, pratiṣṭhā́, níṣikta, víṣita; anuṣvadhám, suṣéka; the cases are numberless.

b. The principle exceptions are in accordance with the principles already laid down: namely, when the root contains an r-element, and when a recurrence of the sibilant would take place. But there are also others, of a more irregular character; and the complete account of the treatment of initial radical s after a prefix would be matter of great detail, and not worth giving here.

c. Not infrequently, the initial s, usually altered after a certain prefix, retains the altered sibilant even after an interposed a of augment or reduplication: thus, aty aṣṭhāt, abhy aṣṭhām, pary aṣasvajat, vy aṣahanta, ny aṣadāma, nir aṣṭhāpayan, abhy aṣiñcan, vy aṣṭabhnāt; vi taṣṭhe, vi taṣṭhire.

d. Much more anomalous is the occasional alteration of initial radical s after an a-element of a prefix. Such cases are ava ṣṭambh (against ni stambh and prati stambh) and (according to the grammarians) ava ṣvan.