यथास्वे यथायथम्

Operational rule vidhi

The word यथायथम् is irregularly formed in the sense of 'respectively, fitly, properly'.

Word by word (padaccheda)

Right context यथास्वे saptamī · ekavacanaSubstitute / term यथायथम् prathamā · ekavacana

Right context Saptamī (7th case): "when X follows", the operation applies to what precedes (1.1.66 तस्मिन्निति निर्दिष्टे पूर्वस्य). Also a condition or domain ("in the sense of").
Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.

Full reading

यथास्वे यथायथम्

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

Commentary

The word यथायथम् is irregularly formed in the sense of 'respectively, fitly, properly'.
What is one's own nature, and whatever is natural to one, that is called यथास्व ॥ In this sense is formed यथायथ꣡म् there being doubling and neuter gender. It is an Indeclinable. As ज्ञाताः सर्वे पदार्था यथायथम् = यथास्वभावं "all objects have been known according to their respective nature". सर्वेषां तु यथायथं यथास्मीयं ॥

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