Degenerate orbitals are two or more orbitals that have exactly the same energy. In molecular orbital theory, for example, the πpx and πpy molecular orbitals of a diatomic molecule are degenerate. When degenerate orbitals are being filled, electrons enter them singly with parallel spins, following Hund's rule.

简并轨道是能量完全相同的两个或多个轨道。例如,在分子轨道理论中,双原子分子的 πpx 与 πpy 分子轨道是简并的。在填充简并轨道时,电子按洪特规则以平行自旋单独进入各轨道。