8.1.66 यद्वृत्तान्नित्यम्

Word by word (padaccheda)

Left context यद्वृतात् pañcamī · ekavacanaSubstitute / term नित्यम् prathamā · ekavacana

Left context Pañcamī (5th case): "after X", the operation applies to what follows (1.1.67 तस्मादित्युत्तरस्य). Also used for limits and sources.
Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.

Dotted words are technical terms, dashed ones pratyāhāras (names for classes of sounds or affixes). Hover or tap one to see its card.

Full reading

यद्वृतात् नित्यम्

Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.

Commentary

In connection with यद् in all its forms, the verb retains its accent always.
The anuvritti of प्रथमा and छन्दसि ceases. The prohibition of nighata, which commenced with न लृट् 8.1.29 is present here also. In what ever sentence the word यद् occurs, that is called यद्वृत्तं ॥ The word वृत्तं denotes here the form of यद् in all its declensions with case affixes. According to Kasika, उतर and उतम are not included, according to Patanjali they should be included. See also the explanation of किंवृत्तं in 8.1.48.

Thus यो भुङ्क्ते꣡, यं भोज꣡यति, येन भुङ्क्ते꣡, यस्मै ददाति, यत् कामास्ते जुहुमः꣡ (Rig Veda X. 121.10) यद्रयङ् वायुर्वा꣡ति (T. S. V. 5. I.I.) यद् वायुः प꣡वते ॥ For the form यद्रयङ् see 6.3.92. Though the sutra is in the Ablative (यद्वृत्तात्) and therefore requires that the verb should immediately follow it, yet in यद्रयङ् वायु र्वाति, the intervention of वायुः does not prevent the operation of this rule, according to the opinion of Patanjali.

Vart:- Optionally when the sense is that of 'wheresoever' or 'whensoever'. The word याथाकाम्यं means यथेच्छं 'as one wishes', without regard of time or space. The nighata is prohibited here also. As यत्र क्व चन यजते तद् देवयजन एव यजते ॥

Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.