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.

---

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

---

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

---

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.

---

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

Now, Double Chooz has added another first to its scientific record by detecting the faint neutrino glow that continues after a nuclear reactor goes dark.

From Science Daily ● Aug. 14, 2026

That measurement helped pave the way for future research into matter-antimatter asymmetries in the neutrino sector.

From Science Daily ● Aug. 14, 2026

Because of limited computing resources, they did not run full neutrino simulations for a one-cubic-meter block of unsegmented scintillator.

From Science Daily ● Jul. 17, 2026

According to the team, compact, dust-rich starburst galaxies undergoing rapid star formation could contribute a substantial share of the high-energy neutrino background.

From Science Daily ● Jun. 19, 2026

As the sensitivity of the neutrino telescope improves, it may become possible to probe nuclear fusion in the deep interiors of the nearby stars.

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

Their analysis indicates that these galaxies may account for as much as 20% of the total population of high-energy neutrinos observed across the Universe.

From Science Daily ● Jun. 19, 2026

Because they are so difficult to detect, neutrinos remain the least understood of all known elementary particles.

From Science Daily ● Jun. 12, 2026

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

From Science Daily ● Jun. 11, 2026

Matter is transparent to neutrinos, which pass almost effortlessly through the Earth and through the Sun.

From "Cosmos" by Carl Sagan