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It's a hyphen, not a minus sign

I think with some equations there is a discontinuity at zero, like tan, but it still makes sense to talk about what happens asymptotically approaching zero and then it matters from which side you approach zero, hence positive and negative zero.

tan does not have a discontinuity at zero. |x|/x does, as does 1/x. tan's is at pi/2 in particular and (n+1/2)pi in general.

Although tan has a set of discontinuities when it jumps between +∞ and -∞ through complex infinity (∞~).

tan(π(x + 0.5)) = ∞~, x ∃ ℤ

(π on my screen doesn't look much like greek pi.)

No typo, spin 0 is a thing.

An example is a helium nucleus in the ground state

Maybe for small values of 0?

;)