I was reading up on the definition of theta- notation and came across this,
The definition of $\Theta(g(n))$ requires that every member $f(n) = \Theta(g(n))$ be asymptotically nonnegative, that is, that $f(n)$ be nonnegative whenever $n$ is sufficiently large.
I'm having a little difficulty understanding what this means.
It means that there is some positive $N$ such that for all $n > N$, we have $f(n) \geq 0$.