In physics, in particular in special relativity and general relativity, a four-velocity is a four-vector in four-dimensional spacetime that represents the relativistic counterpart of velocity, which is a three-dimensional vector in space.
A four-velocity is a four-vector in four-dimensional spacetime. This is in physics. This is in particular in special relativity. This is in particular in general relativity. This dimensional spacetime represents the relativistic counterpart of velocity. Velocity is a three-dimensional vector in space.