6.3.50
हृदयस्य हृल्लेखयदण्लासेषु
Operational rule vidhi
हृद् is substituted for हृदय before लेख and the affixes यत् and अण् and before लास.
Word by word (padaccheda)
Target हृदयस्य ṣaṣṭhī · ekavacanaSubstitute / term हृत् prathamā · ekavacanaRight context लेख- यत्- अण्- लासेषु saptamī · bahuvacana
- Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
- Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.
- 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
हृदयस्य हृत् लेख-
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
हृदयस्य → हृत् / लेख-
Replace hṛdayasya with hṛt when lekha-yat-aṇ-lāseṣu follows. Inherited words (anuvṛtti) may add further conditions.
Commentary
हृद् is substituted for हृदय before लेख and the affixes यत् and अण् and before लास।
Thus हृदयं लिखति = हृल्लेखः, हृदयस्य प्रियं = हृद्यम्, हृदयस्येदम् = हार्दम्, हृदयस्य लासो = हृल्लासः ॥ The word लेख is derived by अण् affix from लिख् ॥ Before the word लेख formed by घञ् affix, this substitution does not take place, as हृदयलेखः ॥ The inclusion of लेख in this sutra proves the existence of this maxim "उत्तरपदाधिकारे प्रत्ययग्रहणे न तदन्तग्रहणम्" See 6.3.17.
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.