One of the EilenbergSteenrod Axioms. It states that, for every pair , there is a natural long exact
sequence

(1) 
where the Map
is induced by the Inclusion Map and
is induced by the
Inclusion Map
. The Map
is called the Boundary Map.
See also EilenbergSteenrod Axioms
© 19969 Eric W. Weisstein
19990525