What does antiparticle mean?
An antiparticle is the mirror-image counterpart of a fundamental or subatomic particle: it has the same mass and lifetime as its partner but carries opposite values for properties such as electric charge. The antiparticle of the electron is the positron, which bears a positive charge; other examples include the antiproton and the antineutron. When a particle encounters its antiparticle, the two annihilate each other, converting their entire mass into energy — usually gamma rays — a process described by Einstein's equation E = mc². The concept emerged from Paul Dirac's relativistic quantum theory in the late 1920s, and the positron was experimentally confirmed shortly afterward. Antiparticles are central to modern particle physics, appearing in cosmic rays, particle accelerators, and medical technologies such as PET scanning. Though chiefly a scientific term, it occasionally appears figuratively to describe something that mirrors another while being its exact opposite.
nounA subatomic particle having the same mass as a given particle but opposite values of certain properties, such as electric charge; when a particle meets its antiparticle, both are annihilated, releasing energy.
- The physical counterpart of an elementary or subatomic particle, equal in mass but opposite in charge and other quantum properties.
- (Figurative, rare) A thing or person that mirrors another with opposite characteristics.
"When an electron collides with its antiparticle, the positron, the two annihilate in a burst of gamma rays."
"Physicists at CERN routinely create antiparticles such as antiprotons in high-energy collisions."
"Every known particle is thought to have a corresponding antiparticle with identical mass but opposite charge."
Regular plural form; commonly used when discussing collections of antimatter particles.
"Antiparticles produced in the collider were steered into a storage ring."
Dirac predicted the existence of antiparticles on paper before anyone had ever seen one — and the positron was discovered within a few years.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of antiparticle
The word derives from the Greek-rooted 'particle' (from Latin particula, 'small part'), prefixed with 'anti-' from Greek anti, meaning 'opposite' or 'against'. It arose in early 20th-century physics following Paul Dirac's theoretical prediction of the positron in 1928–1931, when physicists needed a name for these mirrored counterparts. Related words sharing the same roots include 'particle', 'particular', and 'participle'.
How antiparticle is actually used
Strictly a term of physics, used almost exclusively in scientific, technical, and educational contexts. The figurative use as a mirror-image opposite is rare and informal.
Easily confused with antiparticle
Antimatter is the broader category of matter composed of antiparticles, whereas an antiparticle is a single counterpart of one specific particle.