degeneration

(uncountable) The process or state of growing worse, or the state of having become worse.

(uncountable) That condition of a tissue or an organ in which its vitality has become either diminished or perverted; a substitution of a lower for a higher form of structure.

(uncountable) Gradual deterioration, from natural causes, of any class of animals or plants or any particular organ or organs; hereditary degradation of type.

(countable) A thing that has degenerated.