Material particles that have mass and occupy a finite volume in space are commonly referred to as "fermions." Fermions are a type of elementary particle described by quantum mechanics and are characterized by their intrinsic angular momentum, or spin. They follow the Fermi-Dirac statistics, which dictate their behavior and interactions.
Fermions include particles such as electrons, quarks (which make up protons and neutrons), and neutrinos. These particles are fundamental constituents of matter and have properties like mass, electric charge, and spin. Fermions obey the Pauli exclusion principle, which states that no two identical fermions can occupy the same quantum state simultaneously, resulting in the stability of matter and the formation of atoms.
Fermions differ from another type of elementary particle called "bosons." Bosons, such as photons (particles of light), W and Z bosons, and the Higgs boson, have integer values of spin and obey Bose-Einstein statistics. Unlike fermions, multiple bosons can occupy the same quantum state, leading to phenomena like the formation of coherent states and the behavior of superfluids.
It's worth noting that particles like electrons and quarks are believed to be point-like, meaning they do not have a defined extent in space. However, they are still considered fermions due to their mass and spin properties. The notion of "extent in space" becomes more relevant when considering composite particles made up of fermions, such as protons and neutrons, which have a finite size due to the combination of multiple quarks and gluons within them.