Chelation (from Greek χηλή, chelè, meaning claw; pronounce /kiːˈleɪʃən/) is the binding or complexation of a bi- or multidentate ligand. These ligands, which are often organic compounds, are called chelants, chelators, chelating agents, or sequestering agent. The ligand forms a chelate complex with the substrate. The term is reserved for complexes in which the metal ion is bound to two or more atoms of the chelating agent, although the bonds may be any combination of covalent, coordinate covalent, or ionic bonds.