अचो रहाभ्यां द्वे

Operational rule vidhi

If र् or ह् is present after अच् letter, then a यर् letter occurring after such a र् or ह् is optionally duplicated.

Word by word (padaccheda)

Left context pañcamī · ekavacanaLeft context रहाभ्याम् pañcamī · dvivacanaSubstitute / term द्वे prathamā · dvivacana

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, dashed ones pratyāhāras (names for classes of sounds or affixes). Hover or tap one to see its card.

Full reading

रहाभ्याम् द्वे

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

Commentary

There is reduplication of यर् , i.e. all the consonants except ह after the letters र् and ह् following a vowel.
The word यर् of last sutra is understood here. According to others, the वा is also understood, and this is an optional rule. Thus अर्क्कः, मर्क्कः, ब्रह्म्मा, अपह्न्नुते ॥

Why do we say अचः 'following a vowel'? Observe ह्नुते, ह्मलयति ॥

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