A positron is an antiparticle of a what?

The story behind the answer

A positron is the electron’s antiparticle: it has the same mass and spin but the opposite electric charge (+1 instead of −1) and opposite lepton number. When a positron meets an electron, they annihilate, converting their mass into energy—typically two gamma photons of 511 keV each. Positrons are produced in beta-plus decay inside certain unstable nuclei.

Discovered in 1932 by Carl Anderson in cosmic rays, positrons are now key to PET scans in medical imaging. Memory tip: “positron = positive electron.” For contrast: