Magnetic Dipole
Definition
The basic unit of magnetism — every magnet, from a compass needle to an electron, is a dipole with a north and a south pole.
Technical definition
Dipole moment μ = IA for a current loop; torque τ = μ × B aligns it with the field; potential energy U = −μ·B.
Example
A compass needle is a magnetic dipole — Earth's field exerts a torque twisting it toward north, which is why it settles pointing that way.
Common confusion
No magnetic monopoles have ever been found. Cut a magnet in half and you get two smaller dipoles — never an isolated north pole.