impetus

noun

im·​pe·​tus ˈim-pə-təs 

1

a(1)

: a driving force : impulse

(2)

: incentive, stimulus

b

: stimulation or encouragement resulting in increased activity

2

: the property possessed by a moving body in virtue of its mass and its motion

—used of bodies moving suddenly or violently to indicate the origin and intensity of the motion

Did you know?

Impetus Has Latin Roots

Impetus provides the “why” for something: it can be understood as a driving force (as when winning a competition is the impetus for training), an incentive (as when increased skills serve as an impetus for taking a class), or encouragement (as when difficulties are the impetus for improvements). But its root packs more of a wallop: Latin impetus means “assault” as well as “impetus,” and it comes from impetere meaning “to attack.” (Impetere itself comes from petere, meaning “to go to, seek.”) If these origins seem a tad aggressive for such a genteel-sounding word as impetus, consider phrases and idioms like light a fire under someone and push comes to shove, both used when a strong impetus is provided for someone to act, decide, or accomplish something.

Synonyms

• incentive
• encouragement
• motivation
• stimulus

Examples of impetus in a Sentence

In a revealing comment, Mr. Updike says an impetus for Rabbit, Run was the "threatening" success of Jack Kerouac's On the Road, the signature book of the 1950s Beat Generation, and its frenetic search for sensation. —Dennis Farney, Wall Street Journal, 16 Sept. 1992

But 1939 gave new impetus to the Western with the Cecil B. de Mille railway epic Union Pacific, John Ford's skillful and dramatic Stagecoach,  … and George Marshall's classic comic Western, Destry Rides Again. —Ira Konigsberg, The Complete Film Dictionary, 1987

… new techniques of navigation and shipbuilding enlarged trade and the geographical horizon; newly centralized power absorbed from the declining medieval communes was at the disposal of the monarchies and the growing nationalism of the past century gave it impetus … —Barbara W. Tuchman, The March of Folly, 1984

His discoveries have given impetus to further research.

the reward money should be sufficient impetus for someone to come forward with information about the robbery

Recent Examples on the Web

But another member of the Southeastern Connecticut delegation who served as the bill’s sponsor, Rep. Aundre Bumgardner, D-Groton, said that the Plainfield proposal had been the primary impetus for the bill. —Mark Pazniokas, Hartford Courant, 9 July 2025

Still, Streeter suggested that further pressure from the U.K. regulator could provide the impetus required to accelerate changes within the company. —Karen Gilchrist, CNBC, 8 July 2025

Over time and with the impetus of new technology, trust patterns can shift. —Yasmin Green, Foreign Affairs, 7 July 2025

The threat of having citizenship stripped for opposing the administration is powerful enough to silence many, in a moment when many immigrants feel a personal duty and impetus to speak out to protect family and friends. —Anita Chabria, Los Angeles Times, 1 July 2025

Word History

Etymology

Latin, assault, impetus, from impetere to attack, from in- + petere to go to, seek — more at feather

First Known Use

1641, in the meaning defined at sense 1a(1)

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Kids Definition

impetus

noun

im·​pe·​tus ˈim-pət-əs 

1

a

: a driving force : impulse

b

: incentive

2

: momentum sense 1