>"As a second example of an additional symmetry in empty space, physics works, normally, the same when seen in the mirror. That leads to a very useful [usually, but not always!] conserved quantity called parity.
Parity is somewhat different from momentum."
Related:
https://en.wikipedia.org/wiki/Parity_(physics)
https://www.britannica.com/science/parity-particle-physics
https://www.nobelprize.org/uploads/2018/06/yang-lecture.pdf