Linked from
The 15 pages that link to Parity (physics), each with the reason it gives.
Quantum numberRelated: Parity provides a discrete symmetry label for quantum states.
CP violationRelated: Its combination with charge conjugation defines the symmetry that is violated.
CharmoniumRelated: Parity helps classify charmonium levels and constrain their transitions.
Wigner's theoremBroader topic: Its quantum implementation is a unitary symmetry operator.