deriv SD cv (591) ashtadhyayi.com hei.de L 591 ETT STT a 8.3.60 ALPH OLDHOMEPAGE NEWHOMEPAGE

zAsi;vasi;ghasInAJ ca

शासिॱवसिॱघसीनां च ONPANINI 83060

Replace zAs शास् vas वस् ghas घस् (with S ष् after /iN /ku).

zAs शास् + /kta
→ zis शिस् + ta त by zAsa::idaGh...
→ ziS शिष् + ta त by this rule
→ !**ziSTa- शिष्टॱ by STunASTuH

vas वस् + objectshowing /laT /ta
→ vas वस् + /yak + /ta
→ us उस् + /yak + /ta by vacisvapiy...
→ us उस् + ya य + /te''' by Tita::Atman...
→ uS उष् + ya य + /te''' by this rule
→ !**uSyate उष्यते

ghas घस् + /liT
→ ghaghas घघस् + /liT by liTidhAtor...
→ jhaghas झघस् + /liT by kuhozcuH
→ !**jaghas- जघस् + /liT by abhyAsecarca

**jaghas- जघस् + /liT /jhi
→ jaghas जघस् + /us
→ jaghs जघ्स् + /us by gamahanaj...
→ jaghS जघ्ष् + /us by this rule
→ jakS जक्ष् + /us by kharica
→ !**jakSus जक्षुस्

Looks like this sUtra just changes s स् into S ष् after in;ku इन्कु, is his not an ordinary /Satvam change? What is the need of making this sUtra?

Rule < Adezapraty... only works when the s स् is part of an affix or the start of a Sa-root. It will not turn kusuma कुसुम into kuSuma कुषुम or zis शिस् into ziS शिष्.

In this, /Satvam differs essentially from /Natvam. The /Natvam change applies to everything, thats why brahman ब्रह्मन् + /Gas makes **brahmaNas ब्रह्मणस्.