छन्दस्युभयथा

Operational rule vidhi

In presence of the नाम् प्रत्यय, the last letter of the अङ्ग might or might not be made दीर्घ in वेदाः.

Word by word (padaccheda)

Right context छन्दसि saptamī · ekavacanaIndeclinable उभयथा avyaya

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").
Indeclinable An avyaya such as च "and", वा "optionally", न "not".

Dotted words are technical terms. Hover or tap one to see its card.

Full reading

छन्दसि उभयथा

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

Commentary

In the छन्दस् (Vedas) the finals of तिसृ and चतसृ are found in both ways, before the Genitive 6th-Case plural नाम्।
In some places they are seen as lengthened, in others not. As तिसृण मध्यंदिने or तिसॄणाम मध्यंदिने ॥ So also चतसृणाम् and चतसॄणाम् ॥

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