inertia

What it means

1. countableuncountablenatural sciencesThe property of a body that resists any change to its uniform motion; equivalent to its mass.
2. countablefigurativelyuncountableIn a person, unwillingness to take action.

   Men […] have immense irresolution and inertia.

   1837, Thomas Carlyle, chapter II, in The French Revolution: A History […], volume III (The Guillotine), London: James Fraser, […], →OCLC, book IV (Terror)

   2 more examples

   Not all the surviving veteran chiefs would actually fight. Some remained nominally in the resistance but in practice delayed at their bases, pretexting a lack of ammunition for their uncertain inertia.

   1970 August 12 [1969 January 15], John Womack, Jr., Zapata and the Mexican Revolution, New York: Knopf Doubleday Publishing Group, →ISBN, →LCCN, →OCLC, →OL, page 261

   City had been woeful, their anger at their own inertia summed up when Samir Nasri received a booking for dissent, and they did not have a shot on target until the 66th minute.

   2014 March 9, Jacob Steinberg, “Wigan shock Manchester City in FA Cup again to reach semi-finals”, in The Guardian

   Synonyms: idleness, laziness, sloth, slothfulness

3. countableuncountablemedicineLack of activity; sluggishness; said especially of the uterus, when, in labour, its contractions have nearly or wholly ceased.

In a sentence

Men […] have immense irresolution and inertia.

1837, Thomas Carlyle, chapter II, in The French Revolution: A History […], volume III (The Guillotine), London: James Fraser, […], →OCLC, book IV (Terror)

Where it comes from

1. Latininertia“lack of art or skill, inactivity, indolence”
2. Englishinertia

From Latin inertia (“lack of art or skill, inactivity, indolence”), from iners (“unskilled, inactive”), from in- (“without, not”) + ars (“skill, art”). Something close to the modern physics sense was first used in New Latin by Johannes Kepler.