degeneration degeneration /dɪˌdʒɛnɝˈeɪʃən/

noun

1. () The process of declining from a higher to a lower level of effective power, vitality or essential quality  ( devolution , degeneration )
   the process of declining from a higher to a lower level of effective power, vitality or essential quality
     The degeneration of brain cells leads to the development of neurological diseases.
   The degeneration of brain cells leads to the development of neurological diseases.
   
2. Passing from a more complex to a simpler biological form  ( degeneration , retrogression )
   passing from a more complex to a simpler biological form
   
3. The state of being degenerate in mental or moral qualities  ( decadence , decadency , degeneracy , degeneration )
   the state of being degenerate in mental or moral qualities