An energy band is a continuous range of very closely spaced allowed energy levels, formed when a very large number of atomic orbitals from the atoms of a solid interact and combine. Because the levels are so close together, electrons can move between them almost continuously. The arrangement and filling of these bands determines whether a solid is a conductor, an insulator, or a semiconductor.

能带是由固体中大量原子的原子轨道相互作用、组合而成的、能级极为密集的连续允许能量范围。由于这些能级彼此非常接近,电子几乎可以连续地在其间移动。这些能带的排布和填充决定了固体是导体、绝缘体还是半导体。