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The Collaborative International Dictionary
fermion

fermion \fermion\ n. any particle that obeys Fermi-Dirac statistcs and is subject to the Pauli exclusion principle.

Wiktionary
fermion

n. A particle with totally antisymmetric composite quantum states, which means it must obey the Pauli exclusion principle and hence Fermi–Dirac statistics. They have half-integer spin. Among them are many elementary particles, most derived from quarks. Compare ''boson''.

WordNet
fermion

n. any particle that obeys Fermi-Dirac statistics and is subject to the Pauli exclusion principle

Wikipedia
Fermion

In particle physics, a fermion (a name coined by Paul Dirac from the surname of Enrico Fermi) is any particle characterized by Fermi–Dirac statistics. These particles obey the Pauli exclusion principle. Fermions include all quarks and leptons, as well as any composite particle made of an odd number of these, such as all baryons and many atoms and nuclei. Fermions differ from bosons, which obey Bose–Einstein statistics.

A fermion can be an elementary particle, such as the electron, or it can be a composite particle, such as the proton. According to the spin-statistics theorem in any reasonable relativistic quantum field theory, particles with integer spin are bosons, while particles with half-integer spin are fermions.

Besides this spin characteristic, fermions have another specific property: they possess conserved baryon or lepton quantum numbers. Therefore, what is usually referred as the spin statistics relation is in fact a spin statistics-quantum number relation.

As a consequence of the Pauli exclusion principle, only one fermion can occupy a particular quantum state at any given time. If multiple fermions have the same spatial probability distribution, then at least one property of each fermion, such as its spin, must be different. Fermions are usually associated with matter, whereas bosons are generally force carrier particles, although in the current state of particle physics the distinction between the two concepts is unclear. Weakly interacting fermions can also display bosonic behavior under extreme conditions. At low temperature fermions show superfluidity for uncharged particles and superconductivity for charged particles.

Composite fermions, such as protons and neutrons, are the key building blocks of everyday matter.

Usage examples of "fermion".

The Riemann real part one-half corresponds precisely with the fermion spin of one-half.

In 1976 Daniel Freedman, Sergio Ferrara, and Peter Van Nieuwenhuizen, all then of the State University of New York at Stony Brook, discovered that the most promising were those involving supersymmetry, since the tendency of bosons and fermions to give cancelling quantum fluctuations helps to calm the violent microscopic frenzy.

If your vision could extend a little farther down the ladder of size, you would discover that the atoms are made of fermions and bosons.

The fermions, if you ever found them, would be made of quarks, which themselves occur in several different colors and several different flavors.

Exclusion Principle stated that no two fermions -electrons or quarks - could exist in the same quantum state.

Since supersymmetry ensures that bosons and fermions occur in pairs, substantial cancellations occur from the outset—cancellations that significantly calm some of the frenzied quantum effects.

Like opposite ends of a seesaw, when the quantum jitters of a boson are positive, those of a fermion tend to be negative, and vice versa.

Electrons, protons, neutrons, positrons, muons, and neutrinos all satisfy what is known as Fermi-Dirac statistics, and they are collectively known as fermions.

The classical properties of a fermion were having a spin of half a unit, obeying the Pauli exclusion principle (which kept all the electrons in an atom, and neutrons and protons in a nucleus, from falling together into the same, lowest-energy state), and responding to a 360-degree rotation by slipping 180 degrees out of phase with its unrotated version.