neutrino

American  

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

noun

Physics.

neutrinos plural

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.

Other Word Forms

Noun Inflected Forms

• neutrinos
  plural

Etymology

Origin of neutrino

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

Example Sentences

See Examples For:

neutrino neutrinos

Prof. Arthur McDonald, who received the 2015 Nobel Prize in Physics for the discovery of solar neutrino oscillation, commented on the publication:

From Science Daily ● Jun. 12, 2026

In the end, the researchers found that a realistic population of blazars could plausibly explain the extraordinary neutrino event.

From Science Daily ● May 24, 2026

In 2023, scientists detected a subatomic particle called a neutrino hitting Earth with an energy level so extreme it seemed impossible.

From Science Daily ● Apr. 8, 2026

In a study published in Physical Review Letters, the researchers show how such an event could produce a neutrino with this extraordinary energy.

From Science Daily ● Apr. 8, 2026

The low solar neutrino flux probably does not put our view of stellar nucleosynthesis in jeopardy, but it surely means something important.

From "Cosmos" by Carl Sagan

It conducts research in geology, biology, engineering and physics, the latter encompassing experiments studying dark matter, astrophysics and neutrinos.

From The Wall Street Journal ● Jun. 25, 2026

The experiment is also designed to measure three of the six neutrino mixing parameters with better than 1% precision and to study neutrinos produced by supernovae, Earth's interior, the Sun, the atmosphere, and other sources.

From Science Daily ● Jun. 12, 2026

Recent observations have raised questions that could point toward new physics, including the effects of massive neutrinos, modified gravity, and evolving dark energy.

From Science Daily ● Jun. 11, 2026

The researchers saw this effect while studying simulations that included massive neutrinos.

From Science Daily ● Jun. 11, 2026

These experiments imply that the Sun is dimmer in neutrinos than the calculations predict.

From "Cosmos" by Carl Sagan