Editing Spectrum (topology) (section)

=== Ring spectrum ===
A '''[[ring spectrum]]''' is a spectrum ''X'' such that the diagrams that describe [[ring axioms]] in terms of smash products commute "up to homotopy" (<math>S^0 \to X</math> corresponds to the identity.) For example, the spectrum of topological ''K''-theory is a ring spectrum. A '''[[module spectrum]]''' may be defined analogously.

For many more examples, see the [[list of cohomology theories]].