A root ending in short u , which has no Present characteristic (i.e. the vikaraṇa is dropped by luk elision) gets vṛddhi before a pit sārvadhātuka affix beginning with a consonant, but not if the aṅga (stem) is reduplicated.,
Thus यौति, यौषि, यौमि; नौति, नौषि, नौमि, स्तौति, स्तौषि, स्तौमि ॥ Why ending in उ ? Observe एति, एषि, एमि ॥ Why do we say whose vikarana is elided by लुक्? Observe सुनोति, सुनोषि, सुनोमि ॥ Why beginning with हल् ? Observe यवाणि, रवाणि, the First Person of the Imperative is पित् by 3.4.92. Why before a पित् affix? Observe युतः, रुतः ॥ The augment यासुट् being ङित् 3.4.103, prevents पित् action in अपि स्तुयात् राजानम् ॥ The phrase नाभ्यस्तस्य should be read into the sutra from 7.3.87: therefore Vriddhi does not take place here योयोति तोनोति ॥ Here there is luk-elision of यङ् ॥,