The space is the Banach
space of real or complex sequences tending to zero,
with the supremum norm:
The scalar field is specified by the context. More generally, consists of sequences in
a Banach space
whose norms tend to zero, with the
same supremum convention. In particular,
is the space of square-summable-vector-valued sequences
tending to zero. These spaces appear in the Lipschitz
isomorphism problem.