ब्रह्मणस्त्वः

Operational rule vidhi

The affix त्व comes in the sense of of 'nature or action thereof' after the word ब्रह्मण denoting a kind of होत्रा priest.

Word by word (padaccheda)

Left context ब्रह्मणः pañcamī · ekavacanaSubstitute / term त्वः 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. Hover or tap one to see its card.

Full reading

ब्रह्मणः त्वः

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

Commentary

The affix त्व comes in the sense of of 'nature or action thereof' after the word ब्रह्मण denoting a kind of होत्रा priest.
This debar छ. Thus ब्रह्मणो भावः कर्म वा = ब्रह्मत्वम् ॥ This debars तत् ॥ When ब्रह्मण् means a Brahman, by caste, we have ब्रह्मत्वम् or ब्रह्मता ॥
So much for the province of the affixes मञ् and स्नञ् 4.1.87.

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