Bordism

A relation between compact boundaryless manifolds (also called closed manifolds). Two closed manifolds are bordant iff their disjoint union is the boundary of a compact -manifold. Roughly, two manifolds are bordant if together they form the boundary of a manifold. The word bordism is now used in place of the original term cobordism.

REFERENCES:

Budney, R. "The Bordism Project." http://www.math.cornell.edu/~rybu/bordism/bordism.html