An Etymological Dictionary of Astronomy and Astrophysics

A measure of the → energy of the least tightly held → electrons within a → solid at a → non-zero → temperature.
The value of the Fermi level at → absolute zero (-273.15 °C) is called the → Fermi energy and is a constant for each solid. In other words, the Fermi level is any → energy level having the probability that it is exactly half filled with electrons in the → Fermi-Dirac statistics. Levels of lower energy than the Fermi level tend to be entirely filled with electrons, whereas energy levels higher than the Fermi tend to be empty.

See also: → Fermi; → level.