deriv SD cv (230) ashtadhyayi.com hei.de L 230 ETT STT a 8.2.24 ALPH OLDHOMEPAGE NEWHOMEPAGE

rAt sasya रात्सस्य ONPANINI 82024

After r र्, padafinal consonants stay, except s स्.

Exception to < saMyogAntasy....

So rs र्स् becomes r र् normally, but rk र्क् &c stay. So, this rule allows some /pada to end in r र् + consonant. The only Sanskrit words that end in two consonants are built by this rule.

Example:

Urj ऊर्ज् "strengthen" + /kvip → Urj- ऊर्ज् f "strength", "juice"

This j ज् stays before vowel /sup, as usual, and and becomes Urg- ऊर्ग् by coHkuH चोःकुः elsewhere, without losing the g ग् —

Urj- ऊर्ज् + /su
→ Urj ऊर्ज् by halGyAbbhyodIrgh...
→ Urg ऊर्ग् by coHkuH 6>
→ !**Urk ऊर्क्, normalizing

Exception to the exception — final s स् always falls by < saMyogAntasy..., even after r र् —

pitR- पितृॱ + /Gas
→ pitus पितुस् by Rta::ut
→ piturs पितुर्स् by uraNraparaH
→ !**pitur पितुर् "of father" by < saMyogAntasy...

The original sUtra appears to be saying "rAt रात् (after r र्) sasya सस्य (replace s)". How come you translate it like you do?

"After r र् replace s स्" means "after r replace s with nothing" because we inherit /lopa "with nothing" from < saMyogAntasy....

"After r र् replace s स् with nothing" must mean "but after r र् replace only s स् with nothing and let the other letters be", because otherwise the rule would be useless. See /niyama.