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

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Etymology

Origin of neutrino

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

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Example Sentences

See Examples For:

neutrino neutrinos

Using their precise helium measurement, the researchers were able to calculate the number of neutrino families in the early Universe.

From Science Daily ● Oct. 20, 2026

Making it work was a struggle, but the first neutrino images, captured by an R&D precursor to IceCube, were "the greatest excitement I ever felt about this project," he said.

From Barron's ● Oct. 6, 2026

So began an audacious plan to build a neutrino observatory at the geographic South Pole, with thousands of light sensors embedded deep in the ice.

From BBC ● Oct. 6, 2026

The pattern and timing of that light allow scientists to estimate the direction the neutrino came from — helping them trace its origins in the cosmos.

From BBC ● Oct. 6, 2026

A proposed neutrino observatory at the old Homestake Mine in Lead, South Dakota, would cost $500 million to build–this in a mine that is already dug–before you even look at the annual running costs.

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

By recording these flashes, researchers can identify evidence of neutrinos that would otherwise pass through Earth without leaving a detectable trace.

From Science Daily ● Nov. 2, 2026

Despite their elusive nature, neutrinos occasionally interact with matter through a fundamental force known as the weak interaction.

From Science Daily ● Nov. 2, 2026

The search for neutrinos began long before technology existed to observe them.

From Science Daily ● Nov. 2, 2026

His expertise helps explain what makes neutrinos so unusual and why scientists built an enormous observatory deep within the Antarctic ice to study them.

From Science Daily ● Nov. 2, 2026

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

From "Cosmos" by Carl Sagan

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