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

If you’re retired and wondering when or whether to move, treat the decision as a research project — don’t procrastinate or let inertia take hold.

From MarketWatch ● Jul. 12, 2026

"You have to take responsibility for your happiness and never stay out of resentment or inertia or acceptance," she said.

From Barron's ● Jun. 25, 2026

It further telegraphed the kind of ideological inertia in which Juneteenth — and any other present-day discussion of slavery in America — too easily becomes mired.

From Salon ● Jun. 19, 2026

Because of this enormous planetary inertia, scientists expect sea levels to keep rising for many centuries.

From Science Daily ● May 22, 2026

I sit at the espresso counter and have a cappuccino, to deal with the inertia that’s come over me at the sight of so much sugar-coated self-indulgence.

From "Cat's Eye" by Margaret Atwood

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 Stellman, Louis J. (Louis John)

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 Cummings, E. E. (Edward Estlin)

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

Related Words

• apathy
• laziness
• paralysis
• passivity
• sluggishness