• synonyms


  1. Electricity.
    1. a device for reversing the direction of a current.
    2. (in a DC motor or generator) a cylindrical ring or disk assembly of conducting members, individually insulated in a supporting structure with an exposed surface for contact with current-collecting brushes and mounted on the armature shaft, for changing the frequency or direction of the current in the armature windings.
  2. Mathematics. the element equal to the product of two given elements in a group multiplied on the right by the product of the inverses of the elements.
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Origin of commutator

First recorded in 1830–40; commutate + -or2
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for commutator

Historical Examples of commutator

  • The brushes should be lifted from the commutator while this is being done.

    The Automobile Storage Battery

    O. A. Witte

  • Brushes which bear on the commutator lead to the charging circuit.

  • To these arms the brushes are attached, so that their spring ends engage with the commutator .

  • A commutator, B, permits of establishing or interrupting the current at will.

  • The Commutator is in two parts, which must be insulated from each other.

    How Two Boys Made Their Own Electrical Apparatus

    Thomas M. (Thomas Matthew) St. John

British Dictionary definitions for commutator


  1. a device used to reverse the direction of flow of an electric current
  2. the segmented metal cylinder or disc mounted on the armature shaft of an electric motor, generator, etc, used to make electrical contact with the rotating coils and ensure unidirectional current flow
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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for commutator


1839, agent noun in Latin form from Latin commutare (see commute (v.)).

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Online Etymology Dictionary, © 2010 Douglas Harper

commutator in Science


  1. The arrangement of contact points in an electric motor connecting an external direct current power supply and the rotating electric coils that use the power, used to generate the AC voltages needed by the coils. The commutator is located at the rotating shaft of the motor, where two power contacts are swept underneath two metal brushes, supplying positive and negative voltage to the coils. When the motor has rotated 180 degrees, the power contacts are each moving under the opposite brush, reversing the polarity of the voltage supplied to the coils.
  2. In a group or an algebra, an element of the form ghg-1h-1 where g and h are elements of the group or algebra. If g and h commute, the commutator is the identity element. The commutator is often written [g, h].
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.