perturbation

[pur-ter-bey-shuhn]
noun
1.
the act of perturbing.
2.
the state of being perturbed.
3.
mental disquiet, disturbance, or agitation.
4.
a cause of mental disquiet, disturbance, or agitation.
5.
Astronomy. deviation of a celestial body from a regular orbit about its primary, caused by the presence of one or more other bodies that act upon the celestial body.

Origin:
1325–75; < Latin perturbātiōn- (stem of perturbātiō; see perturb, -ation); replacing Middle English perturbacioun < Anglo-French < Latin, as above

perturbational, adjective
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World English Dictionary
perturbation (ˌpɜːtəˈbeɪʃən)
 
n
1.  the act of perturbing or the state of being perturbed
2.  a cause of disturbance or upset
3.  physics a secondary influence on a system that modifies simple behaviour, such as the effect of the other electrons on one electron in an atom
4.  astronomy a small continuous deviation in the inclination and eccentricity of the orbit of a planet or comet, due to the attraction of neighbouring planets

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Science Dictionary
perturbation   (pûr'tər-bā'shən)  Pronunciation Key 
  1. A small change in a physical system, most often in a physical system at equilibrium that is disturbed from the outside.

  2. Variation in a designated orbit, as of a planet, that results from the influence of one or more external bodies. Gravitational attraction between planets can cause perturbations and cause a planet to deviate from its expected orbit. Perturbations in Neptune's orbit led to the discovery of the object that was causing the perturbation—the planet Pluto. Perturbations in the orbits of stars have led to the discovery of planetary systems outside of our solar system.


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Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

perturbation

in astronomy, deviation in the motion of a celestial object caused either by the gravitational force of a passing object or by a collision with it. For example, predicting the Earth's orbit around the Sun would be rather straightforward were it not for the slight perturbations in its orbital motion caused by the gravitational influence of the other planets. The search for an eighth planet, which culminated in the discovery of Neptune, was undertaken in part because some astronomers believed that the orbit of Uranus was being gravitationally perturbed by some object beyond it.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Now, reacting to a perturbation requires acknowledging that you are indeed dealing with one.
Introduce perturbation to the current logjam and perhaps some good lessons may emerge.
There were no flats and there was not a mutter of perturbation from the muffler.
Our study lends functional support to the idea that perturbation of histone
  methylation promotes cancer.
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