deriv SD cv (299) ashtadhyayi.com hei.de L 299 ETT STT a 7.2.111 ALPH OLDHOMEPAGE NEWHOMEPAGE

ido 'y puMsi इदो ऽय्पुंसि ONPANINI 72111

Replace id इद् (of /idam-) m with ay अय् (before /su).

Only example:

/idam- m + /su
→ idam इदम् + /su (because <<< idamomaH debars <9 tyadAdInAmaH)
→ ayam- अयम् + /su by this rule
→ !**ayam अयम् m "this" by halGyAbbhyodIrgh...

Shouldn't the y य् of this sUtra have disappeared by lopovyorvali?

True, it should of. Now, pretty please, forget about that, just make idoy इदोय् rhyme with "boy" when you chant this sUtra, and don't worry, be happy.

But there isn't a "boy" vowel in Sanskrit!

If you find chanting oy ओय् hard, then chant idoyapuMsi इदोयपुंसि. Works too.