197. A dental surd mute or nasal

A dental surd mute or nasal, or the dental sibilant, when immediately preceded by a ṣ, is everywhere converted into the corresponding lingual.

a. Under this rule, the combinations ṣṭ, ṣṭh, and ṣṇ are very common; ṣṣ is rarely so written, the visarga being put instead of the former sibilant (172): thus, jyótiḥṣu instead of jyótiṣṣu.

b. Much less often, dh is changed to ḍh after final ṣ of a root or tense-stem, with loss of the ṣ or its conversion to ḍ: see 226 c.

c. Those cases in which the final ṣ becomes ṭ before su (e.g. dviṭsú: 226 b) do not, of course, fall under this rule.