Roughly speaking, repeated usage of vocables leads to dispersion. Dispersion brings about a loss of elasticity in the widening of a vocable's extension. The consequence is an attenuation of the lexical form that biases a vocable's use against its original instances.
Functionalization is one of the effects of attenuation that can lead to a loss of feature between functionalized instances of some vocables. An extreme consequence of this is that morphologically distinct vocables, such as or and and which had only wholly disjoint uses at an earlier stage may eventually find themselves interchangeable in some constructions. This increasing loss of feature is what we call attenuation and what physics calls degeneracy.