Inertia is defined as the inclination to do nothing or to remain unchanged. The term can also be used to refer to a property of matter that continues to remain in its state of rest or uniform motion unless acted upon by an external force.
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what is the definition of inertia
inertness, especially with regard to effort, motion, action, and the like; inactivity; sluggishness.
Medicine/Medical lack of activity, especially as applied to a uterus during childbirth when its contractions have decreased or stopped.
The definition of inertia is the resistance any object has to start moving when it is in a stopped position or to change direction when in motion. You can find more information here: http://en.wikipedia.org/wiki/Inertia