neutrino

American  

[noo-tree-noh, nyoo-] / nuˈtri noʊ, nyu- /

noun

Physics.

plural

neutrinos

1. any of the massless or nearly massless electrically neutral leptons. There is a distinct kind of neutrino associated with each of the massive leptons.

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neutrino British  

/ njuːˈtriːnəʊ /

noun

1. physics a stable leptonic neutral elementary particle with very small or possibly zero rest mass and spin 1/ 2 that travels at the speed of light. Three types exist, associated with the electron, the muon, and the tau particle

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neutrino Scientific  

/ no̅o̅-trē′nō /

1. Any of three electrically neutral subatomic particles with extremely low mass. These include the electron-neutrino, the muon-neutrino, and the tau-neutrino.

2. ◆ The study of neutrinos that come to the earth as cosmic rays suggests that neutrinos can transform into each other in a process called neutrino oscillation. For this phenomenon to be theoretically possible, the three neutrinos must have distinct masses; for this reason, many scientists believe that they have mass.

3. See Table at subatomic particle

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neutrino Cultural  

1. An electrically neutral particle that is often emitted in the process of radioactive decay of nuclei. Neutrinos are difficult to detect, and their existence was postulated twenty years before the first one was actually discovered in the laboratory. Millions of neutrinos produced by nuclear reactions in the sun pass through your body every second without disturbing any atoms.

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Closer Look

Neutrinos were not observed until 1955, roughly a quarter of a century after the physicist Wolfgang Pauli first hypothesized their existence on theoretical grounds. Pauli was studying certain radioactive decay processes called beta decay, processes now known to involve the decay of a neutron into a proton and an electron. A certain amount of energy that was lost in these processes could not be accounted for. Pauli suggested that the energy was carried away by a very small, electrically neutral particle that was not being detected. (He originally wanted to name the particle a neutron but didn't publish the suggestion, and a few years later the particle we now know as the neutron was discovered and named in print. The Italian physicist Enrico Fermi then coined the term neutrino, which means “little neutron” in Italian.) Neutrinos are hard to detect because their mass, if they indeed have any, is extremely low, and they possess no electric charge; a chunk of iron a few light-years thick would absorb only about half of the neutrinos that struck it. Nevertheless, neutrinos can be detected, and three different types have been distinguished, each of which is associated with a particular lepton (the electron, the muon, and the taon) with which it is often paired in interactions involving the weak force. Recent analysis of neutrinos emanated by the Sun has suggested that each type of neutrino can spontaneously turn into one of the others in a process of neutrino oscillation, and for theoretical reasons this in turn would require that neutrinos have mass. If so, then despite their light weight, their abundance may in fact mean that neutrinos contribute significantly to the overall mass of the universe.

Etymology

Origin of neutrino

< Italian (1933), equivalent to neutr ( o ) neuter, neutral + -ino -ine ²; coined by E. Fermi

Example Sentences

"Observing the high-energy neutrino was an incredible event," Baker concludes.

From Science Daily • Apr. 8, 2026

Researchers at Indiana University have helped make a significant advance in our understanding of the universe through a partnership between two leading international neutrino experiments.

From Science Daily • Mar. 3, 2026

These two long distance neutrino projects are among the most sophisticated of their kind.

From Science Daily • Mar. 3, 2026

The result clears the way for exploring new possibilities and helps prepare the field for larger and more advanced neutrino experiments.

From Science Daily • Jan. 12, 2026

Very occasionally, a passing neutrino will bang into one of the atomic nuclei in the water and produce a little puff of energy.

From "A Short History of Nearly Everything" by Bill Bryson