2.4.28
हेमन्तशिशिरावहोरात्रे च च्छन्दसि
Operational rule vidhi
Of the compounds हेमन्त-शिशिरौ and अहोरात्रे , the gender is like that of the first word, in the छन्दस् .
Word by word (padaccheda)
Substitute / term हेमन्त- शिशिरौ prathamā · dvivacanaSubstitute / term अहोरात्रे prathamā · dvivacanaIndeclinable च avyayaRight context छन्दसि saptamī · ekavacana
- Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.
- Indeclinable An avyaya such as च "and", वा "optionally", न "not".
- 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").
Full reading
हेमन्त-
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
Commentary
Of the compounds हेमन्त-शिशिरौ and अहोरात्रे , the gender is like that of the first word, in the छन्दस् ।
हेमन्तशिशिरावृतूनां प्रीणामि, अहोरात्रे इदं ब्रूमः ॥
This aphorism debars the general rule given in 2.4.26.
This applies to these words in all cases and numbers, not being confined to them in the dual number, though exhibited in the sutra in the dual number, as :- पूर्वपक्षाश्चितयः, अपरपक्षाः पुरीषम्, अहोरात्राणीष्टकाः 'The white fortnight is fuel-wood, the black fortnight is the dung-cake, and days and nights are bricks (of the altar of sacrifice).'
Why do we say 'in the Vedas'? Observe दुःखे हेमन्तशिशिरे, अहोरात्राविमौ पुण्यौ. In the Vedas the ordinary rules of gender are often set aside; this an individual example of the universally exceptional nature of the Vedic language.
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.