hairy cell leukemia a form of chronic leukemia marked by splenomegaly and by an abundance of abnormal large mononuclear cells covered by hairlike villi (hairy cells) in the bone marrow, spleen, liver, and peripheral blood.
A set of orbitals are said to be degenerate if they all have the same energy. This degeneracy can sometimes be lifted by external electric or magnetic fields.
Degenerate means they have the same energy level. Not all valence electrons are degenerate. For example, flourine has 7 valence electrons with the configuration 1s^2 2s^2 2p^5 There are 2 s-shell electrons and 5 p-shell electrons.