In physics two or more different physical states are said to be<unk>  if they are all at the same<unk><unk> . Physical states differ if and only if they are linearly independent. An<unk><unk>  is said to be<unk>  if it contains two or more different  states.  The number of different states at a particular<unk><unk>  is called the<unk> 's degeneracy.
In quantum theory this usually pertains to electronic configurations and the electron's<unk><unk> s, where different possible occupation states for particles may be related by symmetry.  The usage comes from the fact that<unk>  eigenstates correspond to identical eigenvalues of the Hamiltonian. Since eigenvalues correspond to roots of the characteristic equation, degeneracy here has the same meaning as the common mathematical usage of the word.
If the symmetry is broken by a perturbation, such as applying an external electric field, this can change the<unk> es of the states, causing<unk><unk>  splitting.
In electromagnetics, degeneracy refers to modes of propagation which exist at the same frequency and longitudinal propagation constant.  As an example, for a rectangular waveguide, the TEmn mode is<unk>  to the TMmn mode if m and n are the same for both of them.
Degenerate energy level
Exothermic reaction
Free radical reaction
Cis-trans isomerism
Thermal depolymerization
Organic redox reaction
Hydrogen-deuterium exchange
Equilibrium unfolding