where C is the C -parity operator, and I 2 is the operator associated with the 2nd component of the isospin "vector". G -parity is a combination of charge conjugation and a π rad (180°) rotation around the 2nd axis of isospin space. Given that charge conjugation and isospin are preserved by strong interactions, so is G. Weak and electromagnetic interactions, though, are not invariant under G -parity.