But when one in a line of descent beginning with a father (and reckoning upwards) is alive, the descendant of a grandson or still lower descendant is called yuvan only.,
The word वंश means an uninterrupted series of family descent-or 'a line'. One who occurs in such a line, like father &c, is called वंश्य ॥ When such a vansya is alive, then the descendant of a grandson &c is called Yuvan. The phrase पौत्रप्रभृतपत्य in the sutra should be construed as पौत्रप्रभृतेर् यद् अपत्यम्. 'He who is the descendant of a grandson &c' In the last sutra, however, this phrase पौत्रप्रभृत्यपत्यं was properly construed by putting the word पौत्रप्रभृति in the case of apposition with अपत्यम् meaning \a descendant being a grandson &c.\ Thus the word Yuvan will be applied to a person who is at least fourth in the order of descent, from the propositus with reference to whom the derivative is made. Thus गर्गः being the head, we have गर्गः
-\tअपत्यम् - गार्गिः (son or putra)
-\tअपत्यम् - गार्ग्यः (Gotra)
-\tअपत्यम् - गार्ग्यायणः (Yuvan)
(if Garga or Gargi &c be alive). The force of the word तु, in the sutra is that it will be called Yuvan only, and not Gotra as well.,