A change in the apparent position of an object relative to more distant objects, caused by a change in the observer's line of sight toward the object.
[French parallaxe, from Greek parallaxis, from parallassein, to change : para-, among; see PARA–1 + allassein, to exchange (from allos, other; see al-1 in the Appendix of Indo-European roots).]
par′al·lactic (-lăktĭk) adj.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 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.