भुवो वुग्लुङ्लिटोः

Operational rule vidhi

The verb root 'भू' gets a वुक् आगम when followed by an अजादि-प्रत्यय of लुङ्लकार or लिट्लकार.

Word by word (padaccheda)

Target भुवः ṣaṣṭhī · ekavacanaSubstitute / term prathamā · ekavacanaRight context लुङ्- लिटोः saptamī · dvivacana

Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.
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").

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

Pink letters are it-markers (anubandhas), tags dropped by 1.3.9. Hover or tap one for the rule that marks it, or try the it-letter finder.

Full reading

भुवः वुक् लुङ्-लिटोः

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

As a rewrite rule (sketch from case endings)

भुवः → वुक् / लुङ्- लिटोः

Replace bhuvaḥ with vuk when luṅ-liṭoḥ follows. Inherited words (anuvṛtti) may add further conditions.

Commentary

भू gets the augment व् (वुक्) before the tense-affixes of the Aorist and the Perfect, when beginning with a vowel.
Thus अभूवन्, अभूवम्; बभूव, बभूवतुः, बभूवुः ॥

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