The tendency of objects to resist changes in motion, or more broadly, resistance to change or action in any system.
From Latin 'inertia' meaning idleness or inactivity, from 'iners' (inactive, unskillful). Newton adopted the term for physics in the 17th century, transforming it from a description of laziness to a fundamental law of motion, later extending metaphorically to describe resistance to change in any context.
Newton's appropriation of 'inertia' is one of the most successful semantic shifts in scientific history - he took a word that meant 'laziness' and made it describe one of the universe's most fundamental properties. This linguistic transformation helped people understand that an object's resistance to changing motion isn't laziness but a basic physical principle.
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