Definition of precession in English:

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Pronunciation: /prɪˈsɛʃ(ə)n/


[mass noun] Physics
The slow movement of the axis of a spinning body around another axis due to a torque (such as gravitational influence) acting to change the direction of the first axis. It is seen in the circle slowly traced out by the pole of a spinning gyroscope.
Example sentences
  • Einstein's theory predicts that such gyroscopes will undergo geodetic precession merely because space-time is curved in the planet's vicinity.
  • Even Newtonian physics was unable to give a complete explanation of its orbit: the direction of the axis was found to move by rather more than could be explained by precession and the gravitational attraction of the other planets.
  • As the tailwheel lifts during the takeoff run, gyroscopic precession tries to turn the plane left of centerline.



Example sentences
  • Classical mechanics, in contrast, predicted that the atomic magnets would precess in the field but remain randomly oriented, so the deflections would only broaden (but not split) the beam.
  • If we take a single spin 1/2 particle, and put it in a magnetic field, the spin precesses.
  • Over just a few months they could actually detect the orbit of the binary system precessing, slowly dragging around.


Pronunciation: /prɪˈsɛʃnl/
Example sentences
  • So we are likely to see precessional magnetic switching used for phones and cameras in the near future.
  • The rate of change in the direction of the rotational axis is the ratio of torque to angular momentum and so gives a value for the precessional constant.
  • That is, if some of the Earth's energy were to be diverted into a slightly larger precessional wobble, the rate of spin should slow down slightly as a consequence.


Late 16th century (as a term in astronomy, referring to the precession of the equinoxes): from late Latin praecessio(n-), from praecedere 'go before' (see precede).

For editors and proofreaders

Line breaks: pre|ces¦sion

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