rī is substituted for the final short ṛ of a aṅga (stem) before an affix beginning with y when it is not a kṛt or a sārvadhātuka affix and the Adverbial affix cvi -- abhūtatadbhāve kṛbhvastiyoge sampadyakartari cviḥ [[5.4.50]].,
The anuvritti of क्ङिति is, however, not understood in this sutra; that of च्वि and अकृत्सार्वधातुकयोः is present. Thus मात्रीयति and पित्रीयति with क्यच् (III. I. 8), मात्रीयते, पित्रीयते with क्यङ् (III. I. 11). चक्रीयते with यङ्, मात्रीभूतः with च्वि ॥ The कित् and ङित् not being understood here, we have पितुरागतं = पित्र्यम् 4.3.79, which is thus formed पितृ + यत् = पित्री + य = पित्र + य (ई being elided by 6.4.148). Why do we say short ऋ? Observe चेकीर्यते, from कृ विक्षेपे, with यङ्, ऋत इद् धातोः and हलिच lengthening. निजेगिल्यते from कॄ and गॄ ॥,