original: More formally, vorticity can be related to the amount of "circulation" or "rotation" (or more strictly, the local angular rate of rotation) in a fluid.
simplifications: vorticity is the the local angular rate of rotation in a fluid. Vorticity can be related to the amount of "circulation" or "rotation" in a fluid. Vorticity can be related to the circulation or rotation in a fluid. Vorticity can be related to the amount of "circulation" or "rotation" in a fluid. Vorticity can also be related to the amount of "circulation" or "rotation" (or more strictly, the local angular rate of rotation) in a fluid. More formally, vorticity can be related to the amount of "circulation" or "rotation" in a fluid.  Rotation is actually the local angular rate of rotation. In a fluid, vorticity can be related to the amount of "rotation". Specifically, vorticity is like the amount of circulation in a fluid. Vorticity is related to the amount of rotation in a fluid. Vorticity can be related to the amount of "circulation" or "rotation" in a fluid