inertia

American  

[in-ur-shuh, ih-nur-] / ɪnˈɜr ʃə, ɪˈnɜr- /

noun

• inertias
  plural

1. 

   inertness, especially with regard to effort, motion, action, and the like; inactivity; sluggishness.

   Synonyms:

   laziness, inaction, torpor

2. Physics.

   1. the property of matter by which it retains its state of rest or its velocity along a straight line so long as it is not acted upon by an external force.

   2. an analogous property of a force.

      electric inertia.

3. Medicine/Medical. lack of activity, especially as applied to a uterus during childbirth when its contractions have decreased or stopped.

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inertia British  

/ ɪnˈɜːʃə, -ʃɪə /

noun

1. the state of being inert; disinclination to move or act

2. physics

   1. the tendency of a body to preserve its state of rest or uniform motion unless acted upon by an external force

   2. an analogous property of other physical quantities that resist change

      thermal inertia

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inertia Scientific  

/ ĭ-nûr′shə /

1. The resistance of a body to changes in its momentum. Because of inertia, a body at rest remains at rest, and a body in motion continues moving in a straight line and at a constant speed, unless a force is applied to it. Mass can be considered a measure of a body's inertia.

2. See more at Newton's laws of motion See also mass

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inertia Cultural  

1. In physics, the tendency for objects at rest to remain at rest, and for objects in uniform motion to continue in motion in a straight line, unless acted on by an outside force. (See Newton's laws of motion.)

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Other Word Forms

Derived Forms

• inertial
  adjective
• noninertial
  adjective

Inflected Forms

Nouns

• inertias
  plural

Etymology

Origin of inertia

First recorded in 1705–15; from Latin: “lack of skill, slothfulness”; see inert, -ia

Explanation

Inertia is resistance to change. You hate looking at people's feet and yet you stay in your job as a shoe salesman year after year. Why? Inertia. Inertia is a physics term. Isaac Newtown discovered that a body at rest would stay at rest and a body moving through space would continue moving through space unless an external force (like friction or gravity) caused it to slow down or stop. Sometimes we need an external force to help us get going or to change direction, too, like a friend to tell us to get off the couch or to quit that job at the shoe store.

Example Sentences

See Examples For:

inertia inertias

The newest fear is that artificial-intelligence agents might help to overcome customers’ inertia to leave their money where it is for a while.

From The Wall Street Journal ● Oct. 5, 2026

This inertia is terrible news for the Premier League as a competition.

From BBC ● Sep. 27, 2026

“We’ve kind of been living, in a way, off inertia of this old idea,” he added.

From Los Angeles Times ● Jul. 24, 2026

One is simple inertia — finding a provider can feel overwhelming.

From MarketWatch ● Jun. 26, 2026

Newton discovered the law of inertia, the tendency of a moving object to continue moving in a straight line unless something influences it and moves it out of its path.

From "Cosmos" by Carl Sagan

The pigs on my either hand had by this time overcome their respective inertias and were chomping cheek-murdering chunks.

From The Enormous Room by E. E. (Edward Estlin) Cummings

That as the bird wing is a screw in action, and acts directly between the inertias of the load and the air, the position and operation of the screw, to the load, must imitate it.

From Scientific American Supplement, No. 443, June 28, 1884 by Various

We alternate between spasms of Virtue and comfortable inertias of Don't-care-a-Damn!

From Port O' Gold A History-Romance of the San Francisco Argonauts by Louis J. (Louis John) Stellman

Related Words

• apathy
• laziness
• paralysis
• passivity
• sluggishness