Theorem
Let be the set of components of a space
be the set of components of a space The components of
The components of form a partition of
form a partition of i.e.
i.e. and
and if
if
Proof
Any element belongs to at least one connected subspace i.e. at least one of the
belongs to at least one connected subspace i.e. at least one of the All the
 All the are connected. If
are connected. If for any
for any then x would have to be in some other connected subspace
then x would have to be in some other connected subspace But then
But then - a contradiction. Hence
- a contradiction. Hence for some
for some
Take two sets and
and Suppose
Suppose and
and Then
Then is a connected subset of
is a connected subset of containing both
containing both and
and - a contradiction since
- a contradiction since if
if