1. (used with a sing. verb) The science of matter and energy and of interactions between the two, grouped in traditional fields such as acoustics, optics, mechanics, thermodynamics, and electromagnetism, as well as in modern extensions including quantum mechanics, relativity theory, cryogenics, solid-state physics, particle physics, and plasma physics.
2. (used with a pl. verb) Physical properties, interactions, processes, or laws: the physics of supersonic flight.
3. (used with a sing. verb) Archaic The study of the natural or material world and phenomena; natural philosophy.
[From Latin physica, from Greek (ta) phusika, (the things) of nature, from neuter pl. of phusikos; see PHYSIC.]
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.