Pāṇini sūtras

After an ordinal numeral upto eleven exclusive, comes the affix an, the word retaining its denotation, when a ‘part’ is meant: but not so in the Chhandas.

1. prākप्राक्

   Part	Lexeme	Sandhi form	Meaning	Stem
   pप्	prākप्राक्	prākप्राक्	earlier	prākप्राक्

2. ekādaśabhyaḥएकादशभ्यः

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   eए	ekādaśanएकादशन्	ekādaśabhyaḥएकादशभ्यः	eleven	ekādaśएकादश् + plus abhyãअभ्य̃

3. a+chandasiअ+छन्दसि

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   aअ	aअ	aअ	not	aअ
   cच्	chandasछन्दस्	chandasiछन्दसि	Veda	chandछन्द् + plus asiअसि

Anuvṛtti

1. anअन् 5·3·48

   Part	Lexeme	Sandhi form	Meaning	Stem
   aअ	anअन्	anअन्	anअन्	anअन्