1. Of, relating to, or resembling the physical or orbital characteristics of a planet or the planets.
a. Of or relating to the earth; terrestrial or earthly: measured the planetary tilt in degrees.
b. Of or affecting the entire world; global: a planetary consensus.
3. Wandering; erratic: a planetary life.
4. Being or relating to a gear train consisting of a central gear with an internal ring gear and one or more pinions.
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.