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impedance

American  
[im-peed-ns] / ɪmˈpid ns /

noun

  1. Electricity. the total opposition to alternating current by an electric circuit, equal to the square root of the sum of the squares of the resistance and reactance of the circuit and usually expressed in ohms. Z

  2. Also called mechanical impedance.  Physics. the ratio of the force on a system undergoing simple harmonic motion to the velocity of the particles in the system.

  3. something that impedes; an obstacle or hindrance.

impedance British  
/ ɪmˈpiːdəns /

noun

  1.  Z.  a measure of the opposition to the flow of an alternating current equal to the square root of the sum of the squares of the resistance and the reactance, expressed in ohms

  2. a component that offers impedance

  3. Also called: acoustic impedance.   Za.  the ratio of the sound pressure in a medium to the rate of alternating flow of the medium through a specified surface due to the sound wave

  4. Also called: mechanical impedance.   Zm.  the ratio of the mechanical force, acting in the direction of motion, to the velocity of the resulting vibration

"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
impedance Scientific  
/ ĭm-pēd′ns /

  1. A measure of the opposition to the flow of alternating current through a circuit. Impedance is measured in ohms. The resistance of a circuit to direct current (also measured in ohms) is generally not the same as its impedance, due to the effects of capacitance and induction in and among the components of the circuit.

  2. See also impedance matching

impedance Cultural  

  1. A measure of the apparent resistance posed by an electrical circuit to an alternating current (AC).

Discover More

The term impedance is most often encountered in dealing with antennas and speakers in television, stereo, and radio systems.

Other Word Forms

  • self-impedance noun

Etymology

Origin of impedance

1886; impede + -ance; term introduced by O. Heaviside

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

To evaluate changes in body composition, the researchers used bioelectrical impedance analysis.

From Science Daily • Apr. 9, 2026

The graphene microelectrodes exhibit low impedance and high charge injection, essential attributes for flexible and efficient neural interfaces.

From Science Daily • Jan. 13, 2024

Then there are people whose acid reflux is severe, as measured by the pH impedance study, and despite taking PPIs correctly, still experience painful, breakthrough heartburn.

From Washington Post • Feb. 27, 2023

Samsung has also added a bioelectric impedance sensor, which is designed to measure body fat.

From The Verge • Aug. 18, 2021

The electrical resonance is the more perfectly attained, the smaller the resistance or the impedance of the conducting path and the more perfect the dielectric.

From The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting by Martin, Thomas Commerford

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.