For the two body system there are numerous covariant forms of interaction. The simplest way of looking at these is from the point of view of the gamma matrix structures of the corresponding interaction vertices of the single particle exchange diagrams. For scalar, pseudoscalar, vector, pseudovector, and tensor exchanges those matrix structures are respectively 1 1 1 2 ; γ γ 51 γ γ 52 ; γ γ 1 μ μ γ γ 2 μ μ ; γ γ 51 γ γ 1 μ μ γ γ 52 γ γ 2 μ μ ; σ σ 1 μ μ ν ν σ σ 2 μ μ ν ν , in which σ σ i μ μ ν ν = 1 2 i [ γ γ i μ μ , γ γ i ν ν ] ; i = 1 , 2. The form of the Two-Body Dirac equations which most readily incorporates each or any number of these intereractions in concert is the so-called hyperbolic form of the TBDE. For combined scalar and vector interactions those forms ultimately reduce to the ones given in the first set of equations of this article. Those equations are called the external field-like forms because their appearances are individually the same as those for the usual one-body Dirac equation in the presence of external vector and scalar fields.