kilogram

American  

[kil-uh-gram] / ˈkɪl əˌgræm /

especially British, kilogramme

noun

1. a unit of mass equal to 1,000 grams: the basic unit of mass in the International System of Units (SI). Up until 2019 the kilogram was defined as equal to the mass of an international prototype, a platinum-iridium cylinder kept in Sèvres, France. The kilogram has since been redefined in terms of universal physical constants, including the speed of light and Planck's constant. kg

2. a unit of force and weight, equal to the force that produces an acceleration of 9.80665 meters per second per second when acting on a mass of one kilogram. kg

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kilogram British  

/ ˈkɪləʊˌɡræm /

noun

1. one thousand grams

2. the basic SI unit of mass, equal to the mass of the international prototype held by the Bureau International des Poids et Mesures. One kilogram is equivalent to 2.204 62 pounds

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kilogram Scientific  

/ kĭl′ə-grăm′ /

1. The basic unit of mass in the metric system, equal to 1,000 grams (2.2 pounds).

2. See Table at measurement

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kilogram Cultural  

1. A unit of mass in the metric system, equal to one thousand grams. The weight of a one-kilogram mass is slightly over two pounds.

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Etymology

Origin of kilogram

From the French word kilogramme, dating back to 1790–1800. See kilo-, -gram ²

Example Sentences

There are about 7,500 liters of helium-3 in a kilogram, according to reporting from the Washington Post.

From MarketWatch • Mar. 31, 2026

Helium 3 alone currently trades at more than $20,000 per kilogram, making it one of the most valuable resources on earth.

From BBC • Mar. 31, 2026

Measured levels ranged from nanograms per liter in water to micrograms per kilogram in sediment.

From Science Daily • Mar. 21, 2026

With SpaceX’s forthcoming Starship, launch costs per kilogram are expected to fall to 1% of the costs under the space shuttle.

From The Wall Street Journal • Feb. 3, 2026

I stop at the door and stare back, hoping when I return to check on the toxin, the LD 50 will be 0.000 nanograms per kilogram.

From "The Last Cuentista" by Donna Barba Higuera