in·​er·​tia | \ i-ˈnər-shə, -shē-ə\

Definition of inertia

1a : a property of matter by which it remains at rest or in uniform motion in the same straight line unless acted upon by some external force
b : an analogous property of other physical quantities (such as electricity)
2 : indisposition to motion, exertion, or change : inertness

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Other Words from inertia

inertial \ i-​ˈnər-​shəl , -​shē-​əl \ adjective
inertially \ i-​ˈnər-​sh(ə-​)lē \ adverb

Did You Know?

Inertia is the inherent property of a body that makes it oppose any force that would cause a change in its motion. A body at rest and a body in motion both oppose forces that might cause acceleration. The inertia of a body can be measured by its mass, which governs its resistance to the action of a force, or by its moment of inertia about a specified axis, which measures its resistance to the action of a torque about the same axiss.

Examples of inertia in a Sentence

He blames governmental inertia for the holdup. After 10 years in an unsatisfying job she overcame her inertia and went back to school.

Recent Examples on the Web

The Shed can be seen as an antidote to the boundless loneliness of the internet and the inertia of on-demand streaming. Dodie Kazanjian, Vogue, "Inside The Shed, Manhattan's New State-of-the-Art Cultural Venue," 12 Dec. 2018 The Superintendent of Criminal Investigations, Hideo Nishimura, was tall and even-featured and had probably been handsome in his youth, but the years at the desk showed in his growing corpulence and a certain slowness in breaking inertia. Andrew Liptak, The Verge, "Two unlikely cops are paired up to solve murders in a war-torn Tokyo in Ninth Step Station," 8 Dec. 2018 Given the originality of her oblique style, near-documentary fascination with large families and taste for depicting provincial inertia, Ms. Martel both excites and confounds viewers. J. Hoberman, New York Times, "Lucrecia Martel: A Director Who Confounds and Thrills," 13 Apr. 2018 Currently, he is restrained only by the lingering professionalism of public servants and a few thin threads of institutional inertia. David Roberts, Vox, "The caravan “invasion” and America’s epistemic crisis," 2 Nov. 2018 Anyone who has looked at a smartphone for hours at a time will tell you how how powerful the smartphone-scroll inertia can be. Carrie Battan, Harper's BAZAAR, "Escaping the Seduction of Your Smartphone," 26 July 2018 There’s something very real about the way the shorter days put me into this terrible inertia. Amanda Macmillan,, "How 5 Real Women Cope With Seasonal Affective Disorder," 15 Feb. 2018 The result is political inertia until a new leader emerges with new energy and ideas to forge a new majority. The Editorial Board, WSJ, "Berlin’s Hotel Merkel," 29 Oct. 2018 The biggest challenge for Yamaha is probably inertia. Ezra Dyer, Popular Mechanics, "Testing the Yamaha 210 FSH: The Boat That Blew Up the Formula," 31 Aug. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'inertia.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of inertia

1713, in the meaning defined at sense 1a

History and Etymology for inertia

New Latin, from Latin, lack of skill, from inert-, iners

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Statistics for inertia

Last Updated

23 Dec 2018

Look-up Popularity

Time Traveler for inertia

The first known use of inertia was in 1713

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English Language Learners Definition of inertia

: lack of movement or activity especially when movement or activity is wanted or needed

: a feeling of not having the energy or desire that is needed to move, change, etc.

physics : a property of matter by which something that is not moving remains still and something that is moving goes at the same speed and in the same direction until another thing or force affects it


in·​er·​tia | \ i-ˈnər-shə \

Kids Definition of inertia

1 : a property of matter by which it remains at rest or in motion in the same straight line unless acted upon by some external force
2 : a tendency not to move or change He stayed at the job mostly because of his inertia.


in·​er·​tia | \ in-ˈər-shə, -shē-ə \

Medical Definition of inertia

1a : a property of matter by which it remains at rest or in uniform motion in the same straight line unless acted upon by some external force
b : an analogous property of other physical quantities (as electricity)
2 : lack of activity or movement used especially of the uterus in labor when its contractions are weak or irregular

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Comments on inertia

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tremendous in size, volume, or degree

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