deriv SD cv (109) ashtadhyayi.com hei.de L 109 ETT STT a 8.3.2 ALPH OLDHOMEPAGE NEWHOMEPAGE

atrAnunAsikaH pUrvasya tu vA

अत्रानुनासिकः पूर्वस्य तु वा ONPANINI 83002

The following sUtras nasalize the previous optionally.

This /adhikAra applies down to kAnAmreDite 10>.

Example. The sUtra pumaHkhayyamp... >>>> replaces the m म् of pums पुम्स् with /ru, making purs पुर्स्. This sUtra says that, if we want, we may nasalize the u उ that is just before the /ru —

**pu~skAmA- पुँस्कामाॱ

But if we don't take this option, then anunAsik... >> will compulsorily add M ं after u उ —

**puMskAmA- पुंस्कामाॱ

However, in printed Sanskrit, outside of grammar books, you will find only **puMskAmA- पुंस्कामाॱ, never **pu~skAmA- पुँस्कामाॱ, for some reason.

What reason?

Your guess is as good as mine. Maybe that's because u~s उँस् is a free variation of uMs उंस्, or maybe because typographers did not like to have a /candrabindu movable type.