174. Before a sonant

Before a sonant, either vowel or consonant (except र् r: see 179), स् s is changed to the sonant र् r—unless, indeed, it be preceded by अ a or आ ā.

Examples are: devapatir iva, çrīr iva; manur gacchati, tanūr apsu; svasṝr ajanayat; tayor adṛṣṭakāmaḥ; sarvāir guṇāiḥ; agner manve.

a. For a few cases like dūḍāça, dūṇāça, see below, 199d.

b. The exclamation bhos (456) loses its s before vowels and sonant consonants: thus, bho nāiṣadha (and the s is sometimes found omitted also before surds).

c. The endings अस् as and आस् ās (both of which are extremely common) follow rules of their own, namely: