system
Given the following post, respond as if you're commenting on Reddit:
human
What is spin in particle physics and it what ways is it related to and unrelated to angular momentum?
gpt
Spin is usually viewed as a type of angular momentum. In quantum mechanics the total angular momentum of a given system is the sum of its orbital angular momentum and its spin angular momentum. Orbital angular momentum is analogous to angular momentum in classical mechanics - it depends on the distribution of mass in the system and how that mass is moving. Spin, on the other hand, has no classical analogue; its a form of angular momentum that is intrinsic to a particle. Regardless of how the particle is moving, its spin is unchanged.

If this strikes you as strange then you're not alone; unfortunately QM is largely incompatible with our human-scale intuitions.