1. The process or an instance of regressing, as to a less perfect or less developed state.
2. Psychology In psychoanalytic theory, reversion to an earlier or less mature stage of psychological development.
3. Medicine Subsidence of the symptoms or process of a disease.
4. Statistics A technique for predicting the value of a dependent variable as a function of one or more independent variables in the presence of random error.
5. Astronomy Retrograde motion of a celestial body.
6. Geology A relative fall in sea level resulting in deposition of terrestrial strata over marine strata.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.