Eilenberg–Steenrod axioms

The Eilenberg–Steenrod axioms are a set of axioms in algebraic topology that characterize (reduced) singular homology and cohomology theories. Formulated by Samuel Eilenberg and Norman Steenrod in the mid-20th century, these axioms provide a rigorous framework for what constitutes a generalized homology or cohomology theory. They serve as a foundation for the study of topological spaces through algebraic means.