angular momentum

American  

noun

Physics.

1. the product of the moment of inertia of a body about an axis and its angular velocity with respect to the same axis.

---

angular momentum British  

noun

1. a property of a mass or system of masses turning about some fixed point; it is conserved in the absence of the action of external forces

---

angular momentum Scientific  

/ ăng′gyə-lər /

1. A measure of the momentum of a body in rotational motion. The angular momentum of rigid bodies is conserved; thus, a spinning sphere will continue to spin unless acted on by an outside force. Changes in angular momentum are equivalent to torque. In classical mechanics, angular momentum is equal to the product of the angular velocity of the body and its moment of inertia around the axis of rotation. It is a vector quantity; the vector points up along the axis of counterclockwise rotation. In quantum mechanics, the angular momentum of a physical system is quantized and can only take on discrete values.

2. See also Planck's constant spin

---

Etymology

Origin of angular momentum

First recorded in 1865–70

Example Sentences

One promising direction is a field called orbitronics, which focuses on using the motion of electrons around an atom's nucleus, known as orbital angular momentum, to carry and store information more efficiently.

From Science Daily • Apr. 19, 2026

"There are other ways to generate orbital angular momentum, but this method allows for the use of cheaper, more abundant materials."

From Science Daily • Apr. 19, 2026

For the first time, researchers demonstrated that chiral phonons can directly transfer orbital angular momentum to electrons in a non-magnetic material.

From Science Daily • Apr. 19, 2026

These observations help scientists understand how angular momentum moves through the cosmic web and shapes galaxy structure, rotation, and star formation.

From Science Daily • Dec. 25, 2025

As the gravitational collapse continued, the primordial galaxies spun increasingly faster, because of the conservation of angular momentum.

From "Cosmos" by Carl Sagan