antiparticle
Physics term for a particle with the same mass but opposite charge and other quantum numbers as a corresponding particle.
A positron is the antiparticle of an electron.
When an antiparticle and a particle collide, they annihilate each other.
反物質 is 'antimatter', the substance composed of antiparticles.
Compound of 反 (anti-) and 粒子 (particle), a direct translation of the English 'antiparticle'.