In physics, a Lorentz scalar is a scalar which is invariant under a Lorentz transformation. A Lorentz scalar may be generated from multiplication of vectors or tensors. While the components of vectors and tensors are in general altered by Lorentz transformations, scalars remain unchanged.
Read more about Lorentz Scalar: Energy, Rest Mass, 3-momentum, and 3-speed From 4-momentum, More Complicated Scalars