Karnatakabhashabhushana 5.20

Elision is optional.

For a consonant standing at pause, elision occurs optionally.

navavayaṁ,

navavayasaṁ;

jātavēdaṁ,

jātavēdasaṁ;

uśanaṁ,

uśanasaṁ.

By fixed option (vyavasthitavibhāṣā), in certain cases there is only elision:

nabhaṁ,

manaṁ.

In certain cases there is only the property of ending in a:

divaṁ,

kakubhaṁ.

In certain cases there is only the property of ending in u.

At pause, gemination [occurs]:

vākku,

dikku,

vīruttu,

pariṣattu.