Energy levels for a single-electron chemical species, such as hydrogen, He+ and Li2+ etc.
In this case all electrons within a shell are said to be degenerate.
Electrons in 2s and 2p orbitals would be labeled as being degenerate (though in this case they might not contain any electron).
The reason being that as there is only 1 electron, there is no repulsive
forces to
off-set the electron energy.