गमश्च

Operational rule vidhi

And the affix खच् comes after the verb गम् 'to go' when in composition with a word ending in a case-affix and when the word to be formed denotes a name.

Word by word (padaccheda)

Left context गमः pañcamī · ekavacanaIndeclinable च avyaya

Left context Pañcamī (5th case): "after X", the operation applies to what follows (1.1.67 तस्मादित्युत्तरस्य). Also used for limits and sources.
Indeclinable An avyaya such as च "and", वा "optionally", न "not".

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

गमः च

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

Commentary

And the affix खच् comes after the verb गम् 'to go' when in composition with a word ending in a case-affix and when the word to be formed denotes a name.
As सुतङ्गमः 'Sutangama'. Though the verb गम् could well have been included in the last aphorism, the separation serves the purpose of carrying the anuvritti of गम् into the subsequent sutras.

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