भू-सुवोस् तिङि

As अभूत्, अभूः, अभुवम्; सुवै, सुवावहै, सुवामहै ॥ The सू refers to the Adadi root (21) in which the Present character is dropped, and does not refer to Divadi (24) or Tudadi (115) roots, because there the Present character श्यन् and श intervene between the Personal endings (तिङ्) and the root: and moreover the affixes श्यन् and श are ङित् 1.2.4 and would not cause guna. Why do we say before तिङ्? Observe भवति where the guna takes place before शप् ॥ Why before a sarvadhatuka affix? Observe व्यति भविषीष्ठ, where the Benedictive is not a Sarvadhatuka 3.4.116, and the augment is of course considered as a portion of the personal ending. Why the guna is not prohibited in बोभवीति when the Intensive यङ् is dropped, and the Personal ending is added directly to the root. Because the form बोभूतु in 7.4.65 indicates by implication that guna takes place in यङलुक् except in बोभूतु ॥

But of सू we have सोषुवीति where guna has been prohibited in the Intensive, because there is no jnapaka with regard to it.

The forms सुवै &c are the 1st Person Imperative of सू ॥,