steady state universe
A theoretical model of the universe in which the density of matter is constant over space and time, and the observed expansion of the universe is compensated for by the continuous creation of matter to maintain a constant density. Because of its inability to predict the observed cosmic microwave background radiation, the model has been discredited.
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.