Antiparticles: Twins with Opposite Quantum Numbers

Every particle has a corresponding antiparticle. They have the same mass and spin, while electric charge and several other additive quantum numbers have opposite signs. For example, the positron is the electron's antiparticle: it has the same mass and spin but the opposite charge. Saying antimatter generally has “opposite spin” is not correct; spin is the same, while other quantum numbers change sign.