Fermions

Part of speech: noun

Definitions

1. Subatomic particles that obey Fermi-Dirac statistics and the Pauli exclusion principle, typically making up matter
2. Fundamental or composite particles characterized by half-integer spin and that cannot occupy the same quantum state
3. Particles such as electrons, protons, and neutrons which follow quantum rules preventing identical states among them

Etymology: "Fermions" is the plural of "fermion", a term for particles with half-integer spin, such as electrons, protons and neutrons, that obey the rule that no two can share the same quantum state. The singular was coined in 1945 by the English physicist Paul Dirac, who needed a name for this class of particles and chose to honour the Italian-American physicist Enrico Fermi, whose statistics describe how such particles behave in large groups. The name is built from "Fermi" and the suffix "-on", the same ending used in "electron" and "proton" for subatomic particles. Dirac gave the coinage in a lecture titled "Developments in Atomic Theory", so the word was born in a talk on physics rather than in a dictionary or a textbook.

Synonyms: particles, matter particles, subatomic particles, bosons, quarks