Why do we call the cone of curves(effective one cycles) on a variety $X$ as $NE(X)$, what does $NE$ stand for? 



Where does the name $NE(X)$ come from?
As far as I know, the notation appears first in Mori's landmark paper of 1982. He uses $N(X)$ for the group of 1-cycles modulo **N**umerical equivalence (tensored with $\mathbb{R}$), and then, quite naturally, $NE(X)$ for the convex cone spanned by classes of **E**ffective cycles in $N(X)$.


