What does muon mean?
A muon is an unstable, negatively charged subatomic particle. It belongs to the lepton family, alongside the electron and tau particle, but is much heavier than an electron. Muons are produced in high-energy processes, including collisions in particle accelerators and interactions involving cosmic rays in the atmosphere. Because they are electrically charged, they can be detected through the trails of ionisation they create as they pass through matter. A muon eventually decays into other particles, commonly an electron or muon-neutrino pair. The name comes from the first letter of the Greek word for “middle,” chosen because the muon is intermediate in mass between the electron and the heavier tau. Muons occur naturally in cosmic-ray showers and can also be generated and studied in laboratory accelerators, making them important in particle physics, astrophysics, and the study of matter-antimatter symmetry.
nounA muon is an unstable subatomic particle, similar in electric charge to an electron but about 207 times more massive. It is one of the elementary particles in the Standard Model and decays into other particles, often producing electrons and neutrinos.
- An unstable, negatively charged subatomic particle belonging to the lepton family, with a mean lifetime of about 2.2 microseconds.
"Scientists detected the decay of a muon in the detector and measured the particles released in the process."
"The muon crossed the chamber and left a distinctive trail of ionisation."
"A high-energy muon beam was directed toward the target in the accelerator."
The plural is used when referring to multiple particles of this type.
"The detector recorded thousands of muons during the experiment."
The muon is named after the Greek letter μ, and it is one of the fleeting particles that pass through ordinary matter almost unnoticed.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does muon come from?
The word “muon” was coined in the early twentieth century by combining the Greek letter μ, the initial of the Greek word mesos, meaning “middle,” with the scientific suffix -on. The name reflects the particle’s intermediate mass between the electron and the tau. The spelling and pronunciation follow the conventions of English particle names such as “proton” and “neutron,” although the element in “muon” specifically invokes the Greek letter.
Related word forms
How muon is actually used
The term is a technical particle-physics term and is normally used in specialist scientific contexts. Its spelling and pronunciation are standard in both British and American English.
Easily confused with muon
A muon carries negative electric charge, whereas a neutron is electrically neutral and belongs to the class of particles called baryons.