 Five-term exact sequence

The Five-Term Exact Sequence is a concept in algebraic topology and homological algebra, particularly in the context of derived functors and spectral sequences. It often arises in the study of homology and cohomology theories. In general, an exact sequence is a sequence of algebraic objects (like groups, modules, or vector spaces) linked by homomorphisms where the image of one homomorphism equals the kernel of the next.