Spin is an intrinsic quantum property associated with each particle, which is characteristic of the nature of the particle, just like its mass and its electric charge . It allows us to characterize the behavior of the particle under the effect of its rotational symmetry in space.

Fascinating topic! The relationship between spin and rotational symmetry in space is crucial in understanding particle behavior. This concept has significant implications for cryptography, where quantum keys rely on entangled particles' spin properties to ensure secure communication.