pad is substituted for pāda before the affix yat used in any sense other than that of 'suited there to'.,
Thus पादौविध्यन्ति = पद्याः शर्कराः, पद्याः कण्टकाः ॥ When यत् has the force of \suited there to\ we have पाद्यम् = पादार्थमुदकं ॥ (see 4.4.83 and 5.4.25.
Vart:- Before the affix इक्, in the sense of 'the walks there by', पद is substituted for पाद; as पादाभ्यां चरति = पदिकः 4.4.10 by ष्ठन् affix. The word पाद in this sutra means 'the actual foot', a part of animal organism. Therefore पद् is not substituted before the यत् of (V. I. 34), as द्विपाद्यम्, त्रिपाद्यम् because पाद here denotes, 'a measure'.,