antiparticle

/ˈæntiˌpɑrtɪkəl/
noun
  1. A subatomic particle that has the same mass as another particle but opposite electrical charge or other properties, and that can annihilate the other particle upon contact.
    • When a particle meets its antiparticle, they annihilate each other.
    • The positron is the antiparticle of the electron.
    • Scientists study antiparticles to understand the early universe.
Antonyms
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