An Iitaka fibration of a divisor of nonnegative Iitaka dimension is the rational fibration determined
by its section-ratio field. For a rational Cartier
divisor
on a normal integral projective variety over
, let
where the floor function rounds each divisor coefficient down and the divisorial sheaf is reflexive. The Iitaka
field is generated by ratios of nonzero sections
from the same
,
over all positive integers
with
. In sufficiently large divisible degrees, the image
of the complete system has this function field.
Its dimension is
.