Massey product

The Massey product is a concept from algebraic topology, specifically in the context of homology theory and cohomology. It is named after the mathematician William S. Massey, who introduced the idea. In algebraic topology, cohomology theories provide important algebraic invariants that help classify topological spaces. The Massey product is a way of constructing new cohomology classes from existing ones when working with the cohomology of spaces.