6.4.89
ऊदुपधाया गोहः
Operational rule vidhi
When the उपधा of verb root गुह् has a chance of undergoing a गुणादेश while followed by an अजादिप्रत्यय, the गुणादेश is blocked and the उपधा becomes दीर्घ instead.
Word by word (padaccheda)
Substitute / term ऊत् prathamā · ekavacanaTarget उपधायाः ṣaṣṭhī · ekavacanaTarget गोहः ṣaṣṭhī · ekavacana
- Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.
- Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
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
ऊत् उपधायाः गोहः
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
उपधायाः गोहः → ऊत्
Replace upadhāyāḥ gohaḥ with ūt. Inherited words (anuvṛtti) may add further conditions.
Commentary
For the penultimate ओ of the गुण-ated अङ्ग (stem) गोह् (from गुह्) there is the substituted ऊ before an affix beginning with a vowel.
Thus निगूहति, निगूहकः, साधुनिगूहिन्, निगूहम्, निगूहन्ति, गूहो वर्तते ॥ Why do we say 'penultimate'? So that the substitution should not apply any where else. The form गोह् is taken in the sutra to prohibit the application of the rule to cases where गुह् does not assume the form गोह् ॥ Therefore not here, निजुगुहतुः, निजुगुहुः ॥ This change will not take place before the affixes beginning with a consonant; as निगोढा, निगोढुम् ॥ Some say, the word is exhibited as गोह in order to prohibit the अय् substitution of णि before ल्यप् ॥ As निगाहि + ल्यप् = निगूह्य (6.4.56 not applied), the ऊ substitution being considered as asiddha 6.4.22 would have brought in अय्, गूह् being considered as a word having a light vowel for its penultimate. According to Kasika the ऊ substitution, however, is not asiddha, as their places of operation are different.
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.