retrogression

retrogression (countable and uncountable, plural retrogressions)

1. A deterioration or decline to a previous state.
   • 1849, Hogg's Weekly Instructor (page 388)

     History and experience, the enshriners of the past, and investigation, the discoverer of the present and preparer for the future, will prevent retrogression.

   • 1908, The Three Initiates, The Kybalion: Hermetic Philosophy‎:

     Suns spring into being, and then their height of power being reached, the process of retrogression begins, and after aeons they become dead masses of matter, awaiting another impulse which starts again their inner energies into activity and a new solar life cycle is begun.

2. (biology) A return to a less complex condition.

• retrogressive