atomic mass unit

noun

, Physics.

1. Also called dalton. a unit of mass, equal to 1/12 (0.0833) the mass of the carbon-12 atom and used to express the mass of atomic and subatomic particles.
2. (formerly) a unit of mass, equal to 1/16 (0.0625) the mass of an oxygen atom having atomic mass 16. : amu, AMU

atomic mass unit

noun

1. a unit of mass used to express atomic and molecular weights that is equal to one twelfth of the mass of an atom of carbon-12. It is equivalent to 1.66 × 10 ^–27kg amu Also calledunified atomic mass unitdalton

atomic mass unit

1. A unit of mass equal to 1 12 the mass of an atom of the most common isotope of carbon (carbon 12), which is assigned a mass of 12 and has a value of 1.660 × 10 ^-24 grams. A hydrogen atom has a mass of 1 atomic mass unit since its mass is 1 12 the mass of carbon 12.
2. Also called dalton

Word History and Origins

Origin of atomic mass unit¹

First recorded in 1950–55

Example Sentences

The deuteron mass, md, is then found in atomic mass units, where one atomic mass unit is defined as one-twelfth the mass of the carbon atom.

From Nature

Extrapolating these rates over geologically important periods of time and merging with modeled radiolysis data yields a predicted 1000-fold decrease in 100–atomic mass unit organic molecules in ∼650 million years.

From Science Magazine

Even a short jog can help you shed a few septillion daltons, a unit of mass often used in biochemistry that is equivalent to the atomic mass unit.

From Scientific American