In Newton's theory of gravitation and in various relativistic classical theories of gravitation, such as general relativity, the tidal tensor represents
The tidal tensor represents the relative acceleration due to gravity of two test masses separated by an infinitesimal distance. The component Φ a b {\displaystyle \Phi _{{a}{b}}} represents the relative acceleration in the a ^ {\displaystyle {\hat {a}}} direction produced by a displacement in the b ^ {\displaystyle {\hat {b}}} direction.