  The study of the projective coordinate ring of the (geometric invariant
theory) moduli space of n ordered points on P^1 up to automorphisms began with
Kempe in 1894, who proved that the ring is generated in degree one in the main
(n even, unit weight) case. We describe the relations among the invariants for
all possible weights. In the main case, we show that up to the symmetric group
symmetry, there is a single equation. For n not 6, it is a simple quadratic
binomial relation. (For n=6, it is the classical Segre cubic relation.) For
general weights, the ideal of relations is generated by quadratics inherited
from the case of 8 points. This paper completes the program set out in [HMSV1].
