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

"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

That prefix would also have to remind the AI to obey the laws of physics with wording like: “gravity and inertia respected—mass has real weight, correct contact shadows, no floating props.”

From The Wall Street Journal • May 21, 2026

The proposal was met with bureaucratic inertia and with skepticism from scientists, but the idea persisted in Dr. Knipling’s mind.

From "Silent Spring" by Rachel Carson

Related Words

• apathy
• laziness
• paralysis
• passivity
• sluggishness