159. With the exceptions

With the exceptions above stated, the collision of surd and sonant sounds is avoided in combinations—and, regularly and usually, by assimilating the final to the following initial, or by regressive assimilation.

Thus, in internal combination: átsi, átti, atthás, attá (√ad + si etc.); çagdhí, çagdhvám (√çak + dhi etc.);—in external combination, ábhūd ayám, jyóg jīva, ṣáḍ açītáyaḥ, triṣṭúb ápi, dig-gaja, ṣaḍ-ahá, arcád-dhūma, bṛhád-bhānu, ab-já.