any particle that obeys Fermi-Dirac statistcs and is subject to the Pauli exclusion principle.
a particle with half-integer spin (e.g. electrons, protons, neutrons). Fermions obey the Pauli exclusion principle. The wave function describing a collection of fermions is antisymmetric with respect to the exchange of identical particles.
The term for a particle with half-integer spin. Examples include the quarks and leptons of the Standard Model.
a particle, or patter of string vibration, with half a whole odd number amount of spin; typically a matter particle.