in·​er·​tia | \ i-ˈnər-shə How to pronounce inertia (audio) , -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 How to pronounce inertia (audio) , -​shē-​əl \ adjective
inertially \ i-​ˈnər-​sh(ə-​)lē How to pronounce inertia (audio) \ 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 One study of people whose loans were canceled when the lender lost important paperwork found that the borrowers, freed from the inertia that often accompanies debt, were more likely than other people to move, change jobs and see pay raises. Alana Semuels, Time, "Erasing Student Debt Makes Economic Sense. So Why Is It So Hard to Do?," 1 Apr. 2021 Healthier commodity prices only serve to magnify that natural internal inertia. David Blackmon, Forbes, "The Next U.S. Oil And Gas Boom Suddenly Looms On The Horizon," 5 Mar. 2021 That turns Jasmila Zbanic’s film from entertainment to tragic drama — a white-knuckle portrayal of one woman’s resourcefulness in the face of bureaucratic inertia and certain death. Globe Staff,, "In ‘Quo Vadis, Aida?,’ a final horror in a century filled with horror," 17 Mar. 2021 Absent surprise breakthroughs, inertia appears most likely on two intractable foreign policy challenges that most American presidents try and fail to solve. Stephen Collinson, CNN, "Biden needs a breakthrough with Iran and North Korea," 16 Mar. 2021 This step would help to protect our servicemen and women from having their service misused by shifting the default American posture, which favors extending war through indecision and sheer inertia. Erik Edstrom, The New Republic, "How Biden Can Transform America’s Foreign Policy," 16 Mar. 2021 While around 30% of people had exercised more during the pandemic, 40% were less active, creating a growing physical-activity gap, McKinsey said, urging the industry to come up with a strategy to tackle physical inertia. Adrian Croft, Fortune, "Adidas unveils an ambitious 5-year recovery plan as crosstown rival Puma steals its buzz," 10 Mar. 2021 Thirty-three years later, that restraint feels more like inertia with Akeem more stranded than ever between his lost idealism and his father’s authoritarianism. Los Angeles Times, "Review: Eddie Murphy and Arsenio Hall are back in ‘Coming 2 America.’ It wasn’t worth the wait.," 4 Mar. 2021 If inertia were causing the flowing fountain, the chain would be stationary at the top of the curve, says Biggins, in the same way that a ball tossed into the air is stationary at its highest point. Elizabeth Gibney, Scientific American, "Physicists Explain "Gravity-Defying" Chain Trick," 15 Jan. 2014

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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Time Traveler for inertia

Time Traveler

The first known use of inertia was in 1713

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Statistics for inertia

Last Updated

11 Apr 2021

Cite this Entry

“Inertia.” Dictionary, Merriam-Webster, Accessed 11 Apr. 2021.

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More Definitions for inertia



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 How to pronounce inertia (audio) \

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 How to pronounce inertia (audio) \

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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