The semi-vowel of vyā (vye) 'to cover' is not vocalised when the affix lyap follows.,
As प्रव्याय, उपव्याय ॥ The separation of this sutra from the last, is for the sake of the subsequent sutra, in which the anuvritti व्ये runs.,
व्यश् च
Adhyāya 6 · Pāda 1 · Rule 43