- the mathematical operation of replacing every elementary particle by its antiparticle. Symbol: C
- A reversal of the sign of the charge, the magnetic moment, and other internal quantum numbers of every particle in the system to which it is applied, effectively turning every particle into its antiparticle. In the mathematics of quantum mechanics, this operation is denoted by the operator C. It had long been assumed that charge conjugation, together with parity conjugation, should leave the behavior of a physical system unchanged, but observations of kaon decay suggest this is not always the case. See also conservation law.