The letters C in this abbreviation means conjugation of charges, that is each elementary particle has a twin with an opposite charge: antineutrons, electrons, anti electrons, or positrons, and so on.

字母 C 在这个缩写中意思是电，每个基本粒子都有一个带相反电孪生体：反中子、电子、反电子或正电子等等。