wave-particle duality

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The exhibition of both wavelike and particlelike properties by a single entity, as of both diffraction and linear propagation by light.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The concept applying to all matter and radiation, but most evident in light and particles such as the electron, that properties of waves and of particles are exhibited simultaneously.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (physics) the property of matter and electromagnetic radiation that is characterized by the fact that some properties can be explained best by wave theory and others by particle theory