system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Dark Matter, in grade school we learned "matter" is something that has mass and occupies space. If dark matter doesn't interact with the electro-magnetic force, couldn't regular matter occupy the same space as it?

I'm sure it's just a grade school simplification, like there being only 3 states of matter or 5 senses.
gpt
'Taking up space' in particle physics means being subject to the *Pauli exclusion principle*, which says that certain kinds of particles can't occupy the same state as another, identical particle at the same time. 

This principle applies to particles called *fermions*, which include the quarks that make up protons and neutrons, along with neutrinos and electrons. This doesn't require the particle to have charge - neutrinos don't and are still fermions. It's based, instead, on a property called *spin* - half-integer spins like 1/2 and 3/2 make a particle a fermion, integer spins (like 0, 1, or 2) make a particle a *boson* (that is, not subject to the exclusion principle).

The nature of dark matter isn't known - it may be made of fermions, or not. So we don't know whether it "takes up space" in that sense.