deriv SD cv (294) ashtadhyayi.com hei.de L 294 ETT STT a 8.3.16 ALPH OLDHOMEPAGE NEWHOMEPAGE

ros supi रोः सुपि ONPANINI 83016

But true r stays before /sup'.

Exception to < kharavasAn..., which would turn true r into H ः, then into s स् by vAzari वाशरि, then maybe /Satvam.

(Don't confuse this rossupi रोःसुपि rule with rosupi "ahan अहन् becomes ahar अहर् before nothing".)

**catur- + /sup'
→ catursu , with no < kharavasAn...
→ caturSu "in four", with /Satvam

**gir- + /sup'
→ gIr + su by rvorupadhAy...
→ gIrsu , with no < kharavasAn...
→ **gIrSu "in words", with /Satvam.

Why do we say true r?

The /ru is unaffected by this rule, turns into H by < kharavasAn..., and gets vAzari 20> optionally —

**manas- + /sup' → **manassu or "manaHsu"

**dhanus- + /sup' → **dhanuSSu or "dhanuHSu", either way /sup' gets /Satvam after non-a vowel.

I don't understand how the wording of the original sUtra matches your translation. Shouldn't "ros + supi " mean "replace /ru before /sup'"?

Yes, it does. However that must necessarily mean "replace ONLY /ru before /sup', but not true r". See /niyama.