conserved quantity
(of a dynamical system) function of the dependent variables that is a constant (in other words, conserved) along each trajectory of the system
R-parity
conserved ℤ/2 symmetry in supersymmetric gauge theory, such that standard model particles have R-parity +1 while their superpartners have R-parity −1
good quantum number
quantum number that doesn't change for any eigenstate as time progresses
Zilch
physics term; a conserved quantity of the electromagnetic field