I came across one sentence below, I am not able to see it... Any comment suggestion, reference is welcome. Thanks in advance.
"Let $V$ be a finite dimensional inner product space. The complexification of metric endows $\mathbb C\otimes V$ with a complex quadratic form. And this quadratic form $Q$is degenerate. That is there are nonzero element in $\omega\in\mathbb C\otimes V$ such that $Q(\omega)=0$."
Such elements are called isotropic vector. I can't see it, why these element are called isotropic vector(why this terminology).
Edit: Above sentence I found from Laszlo Lempert paper " loop space as complex manifold" page 533, Last paragraph; where he is making above statement for normal bundle of over a loop....