Sa-smā-smiṃ-saṃ-sāsv attaṃ

1. Assa = ta + sa (“ta” becomes “a” (§176); ‘s’ is inserted (§61)).
2. Asmā = ta + smā (“ta” becomes “a” (§176)).
3. Asmiṃ = ta + smiṃ (“ta” becomes “a” (§176)).
4. Assaṃ = tā + smiṃ (‘ā’ of “tā” is named ‘gha’ (§60); ‘smiṃ’ becomes ‘saṃ’ (§179); ‘s’ is inserted (§62); ‘ā’ of “tā” is shortened (§66); “ta” becomes “a” (§176)).
5. Assā = tā + sa (‘ā’ of “tā” is named ‘gha’ (§60); ‘sa’ becomes ‘sā’ (§179); ‘s’ is inserted (§62); ‘ā’ of “tā” is shortened (§66); “ta” becomes “a” (§176)).

Parallel forms (with §176 applied / not applied):

1. Assa, tassa
2. Asmā, tasmā
3. Asmiṃ, tasmiṃ
4. Assaṃ, tassaṃ
5. Assā, tassā

What is the purpose of saying “the letter ‘t’”? [This sutta does not apply when there is no “t”, such as in:] Amussaṃ, amussā.

What is the purpose of saying “when these [inflections] follow”? [This sutta does not apply when these inflections do not follow, such as in:] Nesu, tesu.