momentum

American  

[moh-men-tuhm] / moʊˈmɛn təm /

noun

plural

momenta, momentums

1. force or speed of movement; impetus, as of a physical object or course of events.

   The car gained momentum going downhill. Her career lost momentum after two unsuccessful films.

2. Also called linear momentum.  Mechanics. a quantity expressing the motion of a body or system, equal to the product of the mass of a body and its velocity, and for a system equal to the vector sum of the products of mass and velocity of each particle in the system.

3. Philosophy. moment.

---

momentum British  

/ məʊˈmɛntəm /

noun

1.  p.  physics the product of a body's mass and its velocity See also angular momentum

2. the impetus of a body resulting from its motion

3. driving power or strength

---

momentum Scientific  

/ mō-mĕn′təm /

plural

momenta

1. A vector quantity that expresses the relation of the velocity of a body, wave, field, or other physical system, to its energy. The direction of the momentum of a single object indicates the direction of its motion. Momentum is a conserved quantity (it remains constant unless acted upon by an outside force), and is related by Noether's theorem to translational invariance. In classical mechanics, momentum is defined as mass times velocity. The theory of Special Relativity uses the concept of relativistic mass. The momentum of photons, which are massless, is equal to their energy divided by the speed of light. In quantum mechanics, momentum more generally refers to a mathematical operator applied to the wave equation describing a physical system and corresponding to an observable; solutions to the equation using this operator provide the vector quantity traditionally called momentum. In all of these applications, momentum is sometimes called linear momentum.

2. See also angular momentum impulse

---

momentum Cultural  

1. In physics, the property or tendency of a moving object to continue moving. For an object moving in a line, the momentum is the mass of the object multiplied by its velocity (linear momentum); thus, a slowly moving, very massive body and a rapidly moving, light body can have the same momentum. (See Newton's laws of motion.)

---

Discover More

Figuratively, momentum can refer to the tendency of a person or group to repeat recent success: “The Bears definitely have momentum after scoring those last two touchdowns.”

Etymology

Origin of momentum

First recorded in 1690–1700; from Latin mōmentum; see moment

Explanation

Momentum is generally used to mean increasing forward motion. A boulder rolling down a hill gains momentum. So does a great idea, a team on a winning streak, or the economy. To find an object's physical momentum you multiply its mass by its velocity. Determining the momentum of the economy or the latest fad is much more difficult. Used figuratively, momentum implies that, like a boulder rolling down a hill, something with momentum will continue moving forward on its own. If you're running for class president, you might want to build momentum by holding a few rallies, passing out flyers and starting a website. Once you have momentum, your opponents won't be able to stop you.

Example Sentences

The S&P 500 tumbled 1.24% on Friday, a day after the benchmark’s relative strength index, a measure of market momentum, topped 78 point.

From Barron's • May 18, 2026

This tends to happen when “there’s a big focus on momentum stocks” in a concentrated index, Goepfert said.

From MarketWatch • May 18, 2026

OpenAI is also seeking a public listing and is trying to regain momentum as rival Anthropic has emerged as a presumptive front-runner.

From The Wall Street Journal • May 18, 2026

The IMF said the UK economy had entered the latest global shock with "more momentum than expected".

From BBC • May 18, 2026

Operation Save Sir Fig Newton was picking up momentum, approaching the speed of light.

From "Sir Fig Newton and the Science of Persistence" by Sonja Thomas

Related Words

• energy
• power
• strength