positron

/ˈpɑzɪtrɑn/
noun
  1. A subatomic particle with the same mass as an electron but a positive charge; the antimatter counterpart of the electron.
    • Scientists study positrons to understand the nature of antimatter.
    • When a positron meets an electron, they annihilate each other, releasing energy.
    • Positron emission tomography, or PET scans, use positrons to create images of the body.