Full Idea
Spin is a quantum-mechanical property of a particle akin to rotation about its own axis. Particles of different spins respond to magnetic fields in different ways, so it is a relatively easy thing to measure.
Gist of Idea
Spin is akin to rotation, and is easily measured in a magnetic field
Source
New Scientist writers (Why the Universe Exists [2017], 04)
A Reaction
I wish I knew what 'akin to' meant. Maybe particles are not rigid bodies, so they cannot spin in the way a top can? It must be an electro-magnetic property. Idea 21166 says spin has two possible directions.
Book Reference
New Scientist writers: 'Why the Universe Exists' [John Murray 2017], p.84