6.1.132
एतत्तदोः सुलोपोऽकोरनञ्समासे हलि
Operational rule vidhi
Except for the नञ् समास, when a form of एतद्/तद् word which does not contain a ककार is followed by a सुँ-प्रत्यय which in turn is followed by a व्यञ्जन. the सुँ-प्रत्यय gets removed in the context of संहिता.
Word by word (padaccheda)
Target एतत्- तदोः ṣaṣṭhī · dvivacanaSubstitute / term सुलोपः prathamā · ekavacanaTarget अकोः ṣaṣṭhī · dvivacanaRight context अ- नञ्समासे saptamī · ekavacanaRight context saptamī · ekavacana
- 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").
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
एतत्-
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
एतत्-
Replace etat-tadoḥ akoḥ with sulopaḥ when a-nañsamāse hali follows. Inherited words (anuvṛtti) may add further conditions.
Commentary
After एतद् and तद् there is elision of the case-affix स् (of the Nominative Singular), when a consonant follows it, when these words are not combined with क (5.3.71) and have not the Negative Particle in composition.
Thus एषः + ददाति = एष ददाति, स ददाति, एष भुङ्क्ते, स भुङ्क्ते ॥ Why do we say of एतद् and तद्? Observe यो ददाति, यो भुङ्क्ते ॥ Why do say "the case affix of the Nominative singular?" Observe एतौ गावौ चरतः ॥ Why do we say 'without क'? Observe एषको ददाति, सको ददाति ॥ The words एतद् and तद् with the affix अद्यच्, which falls in the middle, would be considered just like एतत् and तद् without such affix, and in fact would be included in the words एतद् and तद्, hence the necessity of the prohibition. The general maxim is: तन्मध्यपतितस्तद् ग्रहणेन गृह्यते 'any term that may be employed in Grammar denotes not merely what is actually denoted by it, but it denotes also whatever word-form may result when something is inserted in that which is actually denoted by it".
Why do we say "when not compounded with the negative particle"? Observe अनेषो ददाति, असो ददाति ॥ In the compound with the negative particle नञ्, the second member is the principal and takes the case affixes. Why do we say 'when followed by a consonant'? Observe एषोऽत्र, सोऽत्र ॥
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.