An ample line bundle on a proper variety over a field is a line bundle 
such that some positive tensor power gives a closed embedding
into projective space by its global sections.
A line bundle giving such an embedding is very ample.
For a compact complex manifold, the analogous
definition uses a holomorphic embedding.
On projective space, 
is very ample, and 
is ample for every positive integer 
. On a smooth projective curve, a line
bundle is ample precisely when its degree is positive. Ampleness is stronger
than semiampleness, which permits the map defined by a positive tensor power to have
positive-dimensional fibers.
