[ in-ur-shuh, ih-nur- ]
See synonyms for inertia on
  1. inertness, especially with regard to effort, motion, action, and the like; inactivity; sluggishness.

  2. Physics.

    • 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.

    • an analogous property of a force: electric inertia.

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

Origin of inertia

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

Other words for inertia

Other words from inertia

  • in·er·tial, adjective
  • non·i·ner·tial, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use inertia in a sentence

British Dictionary definitions for inertia


/ (ɪnˈɜːʃə, -ʃɪə) /

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

  2. physics

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

    • an analogous property of other physical quantities that resist change: thermal inertia

Derived forms of inertia

  • inertial, adjective

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for inertia


[ ĭ-nûrshə ]

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

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for inertia


[ (i-nur-shuh) ]

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.)

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.