An elementary particle identical to another elementary particle in mass but opposite to it in electric and magnetic properties that when brought together with its counterpart produces mutual annihilation.

【理】反粒子。自然界每一种粒子都有与之对应的反粒子，也有少数粒子自己是自己的反粒子，例如光子。粒子与其反粒子具有许多相同之处，例如质量、自旋、半生期，但也有许多值，例如电荷、磁矩、奇异数，正负号刚好相反。