If mass and energy are different manifestations of the same thing (E = mc^2), what is the larger group that they are both subsets of called?
I believe momentum and inertia also fit in with those two. I would guess that they are subsets of mass. (So I guess mass wouldn’t be included in the list). But I’m just taking a guess.
Mass-energy.
The amount of inertia is the amount of mass. Momentum is approx mass time velocity for small velocities.
momentum is an operator.
Energy and mass aren’t really the same thing: M[sup]2[/sup]C[sup]4[/sup] = E[sup]2[/sup] - P[sup]2[/sup]C[sup]2[/sup] (or, with C==1, M[sup]2[/sup] = E[sup]2[/sup] - P[sup]2[/sup]) where P is momentum.
A question anlogous to the OP would be to ask, “Since speed and velocity are different manifestations of the same thing, what is the larger group that speed and velocity are subsets of?”. I’m not sure that this has a satisfying answer.
Is this an accepted physics term? I thought it your own invention.
In actual usage in relativity, “energy” is usually used as the generic term, and can roughly be broken down into “mass” and “kinetic energy”. Yes, there’s potential energy, but that’s actually part of “mass”, and thermal energy is part of “kinetic”.
Outside of relativity, the terminology is different, but then, outside of relativity, you’re not usually worrying about E = mc[sup]2[/sup].