Before an affix beginning with a y and having an indicatory k or ṅ there is substituted ay for the ī of śī,
As शय्यते with यक्, शाशय्यते with यङ्, प्रशय्य and उपशय्य with ल्यप् which being the substitute of क्त्वा in कित् ॥ But शिश्ये where the affix is ए, and शेयम् where the affix is यत् (neither कित् or ङित्) ॥,