deriv SD cv (351) ashtadhyayi.com hei.de L 351 ETT STT a 7.1.30 ALPH OLDHOMEPAGE NEWHOMEPAGE

bhyaso 'bhyam

भ्यसो ऽभ्यम् ONPANINI 71030

Replace fourth /bhyas with abhyam अभ्यम् (after /yuSmad- /asmad-).

/yuSmad- + fourth /bhyas
→ yuSma युष्म + /bhyas by zeSelopaH
→ yuSma युष्म + abhyam अभ्यम् by this rule
→ yuSm युष्म् + abhyam अभ्यम् by atoguNe
→ !**yuSmabhyam युष्मभ्यम्

/yuSmad- + /bhyas
→ !**asmabhyam अस्मभ्यम्, same steps.

For the singular, see **tubhyam तुभ्यम्, **mahyam मह्यम्.

For the dual see **yuvAbhyAm युवाभ्याम्, **AvAbhyAm आवाभ्याम्.

The sUtra just says "/bhyas". How do you know this applies only to fourth /bhyas and not to fifth /bhyas?

Because of the exception paJcamyA::at >.

Why doesn't bahuvacan... make e ए?

Because the affix is abhyam अभ्यम्, not bhyam भ्यम्.

This sUtra is chanted as bhyasobhyam भ्यसोभ्यम्, so how can you be sure that it splits as bhyAsas भ्यासस् + abhyam अभ्यम् as opposed to bhyasas भ्यसस् + bhyam भ्यम्?

See candravasu's explanation. It ain't pretty, but it works.

Urgh. Sure not pretty. But why didn't /pANini just say abhyam bhyasaH अभ्यं भ्यसः to save us all that trouble?

Maybe because bhyasobhyam भ्यसोभ्यम् is shorter than abhyambhyasaH अभ्यंभ्यसः. See shuffle principle. Or maybe because /pANini likes to say the replaced first and the replacement afterwards, see eruH, atoyeyaH.