The augment yuk (y) is added to the verbal stems 1. śā 2. chā 3. sā 4. hvā 5. ve and 6. pā before the affix ṇi (Causative).,
As निशाययति, अवच्छाययति, अवसाययति, ह्वाययति, संव्याययति, वाययति, and पाययति ॥ The word पा includes the root पा 'to drink'. (Bhuadi 972) पे 'to dry' (Bhuadi 968). but not पा 'to protect' (Adadi 47): because the latter looses the शप् vikarana.
Vart:- The root पा 'to protect' takes the augment लुक् before णि, as पालयति ॥
Vart:- The roots घुञ् and प्रीञ् take the augment नुक् before णि, as धूनयति, प्रीणयति ॥
All these augments are added to the roots, in order that 7.4.1 should cause the shortening of the vowel preceding these. Thus the Aorist of the above are: अशीशयत्, अपीपलत्, अदूधुनत्, अपीप्रिणत् ॥
The roots शा, छा, सा, ह्वा, व्या and पा are exhibited as ending in long आ their Dhatupatha forms are श, शो, छो, सै, सो, ह्वे, व्ये and पै ॥ This indicates that these roots would have taken पुक् by the last sutra, the word आत् 'ending in long आ' means the roots which actually end in long आ, as well as those which get long आ by 6.1.45. This also indicates, that in this subdivision or section, the maxim of lakshana pratipadokta &c does not apply. Therefore when the roots इ with अपि, and जि assume the form अधि-आ and जा before the affix णि by (VI. I. 48), the augment पुक् is added to them, thus अध्यापयति, जापयति ॥,