Definition of "regression"

regression

/ɹɪˈɡɹɛʃ.ən/

noun
countable and uncountable, plural regressions
1. An action of regressing, a return to a previous state.
  Quotations
  Few of these groups or communities that are classed as "savage" show no traces of regression from a more advanced cultural stage.
  1899, Thorstein Veblen, The Theory of the Leisure Class […] ‎, New York: Macmillan
2. An action of travelling mentally back in time.
  Quotations
  I have done past life regressions on my own through self-hypnosis techniques that I learned in Brian Weiss's book Many Lives, Many Masters as well as with past life regression tapes.
  2001, Carol DeCuffa, In Search of Home: An Essential Guide for the Evolving Soul‎
3. (psychotherapy) A psychotherapeutic method whereby healing is facilitated by inducing the patient to act out behaviour typical of an earlier developmental stage.
4. (statistics) An analytic method to measure the association of one or more independent variables with a dependent variable.
  Quotations
  Supervised learning problems are categorized into "regression" and "classification" problems. In a regression problem, we are trying to predict results within a continuous output, meaning that we are trying to map input variables to some continuous function.
  , (Please provide the book title or journal name)‎
5. (statistics) An equation using specified and associated data for two or more variables such that one variable can be estimated from the remaining variable(s).
6. (programming) The reappearance of a bug in a piece of software that had previously been fixed.
7. (medicine) The diminishing of a cellular mass like a tumor, or of an organ size.
8. (exercise) The making an exercise less straining to perform by manipulating the details of its performance like loaded weight, range of motion, angle, speed.