The Fermi energy is defined as
where specifies the number of particles in a particular system at temperature T, and k is Boltzmann's constant (Eisberg and Resnick 1985, pp. 384-385).
A number of quantities are defined is terms of the Fermi energy, including the Fermi momentum, Fermi temperature, and Fermi velocity.
Fermi Momentum, Fermi Temperature, Fermi Velocity, Fermion, Infinite Square Potential Well
References
Eisberg, R. and Resnick, R. Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles, 2nd ed. New York: Wiley, 1985.