purely spacelike parts to the 3d stress tensor. The electromagnetic field tensor combines the electric field and E and magnetic field B The electromagnetic displacement tensor combines the electric displacement field D and magnetic field intensity H as follows The magnetization-polarization tensor combines the P and M fields The three field tensors are related by which is equivalent to the definitions of the D and H fields. The electric dipole moment d and magnetic dipole moment μ of a particle are unified into a single tensor The Ricci curvature tensor is another second-order tensor. Higher-order tensors In general relativity, there are curvature tensors which tend to be higher order, such as the Riemann curvature tensor and Weyl curvature tensor which are both fourth order tensors. See also Spin tensor Tetrad (general relativity) References Tensors Theory of relativity Special relativity General relativity