Cauchy sequence
A sequence![]()
in a metric space is a Cauchy sequence
![]()
if, for every real number , there exists a natural number
![]()
such that whenever .
Likewise, a sequence in a topological vector space![]()
is a Cauchy sequence if and only if for every neighborhood of , there exists a natural number such that for all . These two definitions are equivalent
![]()
when the topology
![]()
of is induced by a metric.