सभा राजामनुष्यपूर्वा

Operational rule vidhi

A तत्-पुरुष compound ending with the word सभा 'court' is neuter, provided that it is preceded by (a word synonymous with) the word राजा or by a word denoting a non-human-being.

Word by word (padaccheda)

Substitute / term सभा prathamā · ekavacanaSubstitute / term राज- अ- मनुष्य- पूर्वा prathamā · ekavacana

Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.

Full reading

सभा राज-अ-मनुष्य-पूर्वा

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

Commentary

A तत्-पुरुष compound ending with the word सभा 'court' is neuter, provided that it is preceded by (a word synonymous with) the word राजा or by a word denoting a non-human-being.
As इनसभम् 'the King's Court.' ईश्वरसभम् 'Lord's Court.'

But in राजसभा 'the King's Court,' the word is not neuter; for synonyms of राजा are only to be taken and not the word-form राजा; an apparent exception to Rule 1.1.68.

So also रक्षःसभम् 'the Court of the Rakshasas' पिशाचसभम् 'the Court of the Pisachas.'

But in काष्ठसभा, दैवदत्तसभा &c, the word is not neuter; for the word non-human has a technical significance meaning Rakshasa or a monster.

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