Sabbato ko

1. Sabbako = sabba + si (‘ka’ is inserted (§178); ‘si’ becomes ‘o’ (§104); ‘a’ of ‘ka’ is elided (§83)).
2. Yako = ya + si (‘ka’ is inserted (§178); ‘si’ becomes ‘o’ (§104); ‘a’ of ‘ka’ is elided (§83)).
3. Sako = sa + si (‘ka’ is inserted (§178); ‘si’ becomes ‘o’ (§104); ‘a’ of ‘ka’ is elided (§83)).
4. Amuko = amu + si (‘ka’ is inserted (§178); ‘si’ becomes ‘o’ (§104); ‘a’ of ‘ka’ is elided (§83)).
5. Asuko = amu + si (‘m’ of “amu” becomes ‘s’ (§173); ‘ka’ is inserted (§178); ‘si’ becomes ‘o’ (§104); ‘a’ of ‘ka’ is elided (§83)).

What is the purpose of saying “optionally”? [To allow exceptions to this rule, such as in:] Sabbo, yo, so, ko.

What is the purpose of saying “after the pronouns”? [This sutta does not apply when there are no pronouns, such as in:] Puriso.

By taking “sabbato” again, ‘ka’ is also inserted in other [places]. Examples: Hīnako, potako.