Today, we will look at the steps to derive the प्रथमा, विभक्तिः, एकवचनम् रूपम् (Nominative singular form) of ‘कर्ण’ (भगवद्गीता 1.8).

1. कर्ण (Gets the प्रातिपदिक संज्ञा by अर्थवदधातुरप्रत्ययः प्रातिपदिकम्। 1.2.45)

2. कर्ण + सुँ (By स्वौजसमौट्छष्टाभ्याम्भिस्ङेभ्याम्भ्यस्ङसिभ्याम्भ्यस्ङसोसाम्ङ्योस्सुप् 4.1.2, the प्रत्ययs सुँ etc. are mandated after कर्ण, since it has the प्रातिपदिक संज्ञा. The sutram in turn is under the अधिकार सूत्रs प्रत्ययः। 3.1.1, परश्च। 3.1.2 and ङ्याप्प्रातिपदिकात्। 4.1.1. The entire term, along with the pratyaya gets the पद संज्ञा by सुप्तिङन्तं पदम्। 1.4.14)

3. कर्ण + स् (उँ gets the इत् संज्ञा by उपदेशेजनुनासिक इत्। 1.3.2 and it takes लोप by तस्य लोपः। 1.3.9)

4. कर्ण + रुँ (रुँ आदेश by ससजुषो रुँ:। 8.2.66. रुँ is an आदेश for the entire पदम् कर्णस् by the rule येन विधिस्तदन्तस्य। 1.1.72. But only the final letter is replaced because of अलोन्त्यस्य। 1.1.52)

5. कर्ण + र् (उँ gets the इत् संज्ञा by उपदेशेजनुनासिक इत्। 1.3.2 and it takes लोप by तस्य लोपः। 1.3.9)

6. कर्णः (रेफ gets विसर्ग आदेश by खरवसानयोर्विसर्जनीयः। 8.3.15, since it is a stop in the utterance and is not followed by any other word)