The a is substituted for the final of śvi in the Aorist aṅ,
As अश्वत्, अश्वताम्, अश्वन् ॥ For the अ of the stem and the अ of the affix, there is the single substitute of the last by 6.2.97. See (III. I. 58).,
Adhyāya 7 · Pāda 4 · Rule 18
The a is substituted for the final of śvi in the Aorist aṅ,
As अश्वत्, अश्वताम्, अश्वन् ॥ For the अ of the stem and the अ of the affix, there is the single substitute of the last by 6.2.97. See (III. I. 58).,