The sphī is the substitute of sphāya 'to swell', the niṣṭhā affixes follow.,
Thus स्फीतः, स्फीतवान् ॥ Why do we say \when the Nishtha affixes follow\? Observe स्फातिः formed by क्तिन् ॥ In the phrase स्फाती भवति, the word स्फाती is the feminine of the word स्फाति formed by क्तिन् ॥ The phrase निष्ठायाम् \when the Nishtha follows\ governs all the subsequent sutras up to (VI. I. 29).,