AskDefine | Define weight

The Collaborative Dictionary

Weight \Weight\, n. [OE. weght, wight, AS. gewiht; akin to D. gewigt, G. gewicht, Icel. v[ae]tt, Sw. vigt, Dan. v[ae]gt. See Weigh, v. t.] [1913 Webster]
The quality of being heavy; that property of bodies by which they tend toward the center of the earth; the effect of gravitative force, especially when expressed in certain units or standards, as pounds, grams, etc. [1913 Webster] Note: Weight differs from gravity in being the effect of gravity, or the downward pressure of a body under the influence of gravity; hence, it constitutes a measure of the force of gravity, and being the resultant of all the forces exerted by gravity upon the different particles of the body, it is proportional to the quantity of matter in the body. [1913 Webster]
The quantity of heaviness; comparative tendency to the center of the earth; the quantity of matter as estimated by the balance, or expressed numerically with reference to some standard unit; as, a mass of stone having the weight of five hundred pounds. [1913 Webster] For sorrow, like a heavy-hanging bell, Once set on ringing, with his own weight goes. --Shak. [1913 Webster]
Hence, pressure; burden; as, the weight of care or business. "The weight of this said time." --Shak. [1913 Webster] For the public all this weight he bears. --Milton. [1913 Webster] [He] who singly bore the world's sad weight. --Keble. [1913 Webster]
Importance; power; influence; efficacy; consequence; moment; impressiveness; as, a consideration of vast weight. [1913 Webster] In such a point of weight, so near mine honor. --Shak. [1913 Webster]
A scale, or graduated standard, of heaviness; a mode of estimating weight; as, avoirdupois weight; troy weight; apothecaries' weight. [1913 Webster]
A ponderous mass; something heavy; as, a clock weight; a paper weight. [1913 Webster] A man leapeth better with weights in his hands. --Bacon. [1913 Webster]
A definite mass of iron, lead, brass, or other metal, to be used for ascertaining the weight of other bodies; as, an ounce weight. [1913 Webster]
(Mech.) The resistance against which a machine acts, as opposed to the power which moves it. [Obs.] [1913 Webster] Atomic weight. (Chem.) See under Atomic, and cf. Element. Dead weight, Feather weight, Heavy weight, Light weight, etc. See under Dead, Feather, etc. Weight of observation (Astron. & Physics), a number expressing the most probable relative value of each observation in determining the result of a series of observations of the same kind. [1913 Webster] Syn: Ponderousness; gravity; heaviness; pressure; burden; load; importance; power; influence; efficacy; consequence; moment; impressiveness. [1913 Webster]
Weight \Weight\, v. t. [imp. & p. p. Weighted; p. pr. & vb. n. Weighting.] [1913 Webster]
To load with a weight or weights; to load down; to make heavy; to attach weights to; as, to weight a horse or a jockey at a race; to weight a whip handle. [1913 Webster] The arrows of satire, . . . weighted with sense. --Coleridge. [1913 Webster]
(Astron. & Physics) To assign a weight to; to express by a number the probable accuracy of, as an observation. See Weight of observations, under Weight. [1913 Webster]
(Dyeing) To load (fabrics) as with barite, to increase the weight, etc. [Webster 1913 Suppl.]
(Math.) to assign a numerical value expressing relative importance to (a measurement), to be multiplied by the value of the measurement in determining averages or other aggregate quantities; as, they weighted part one of the test twice as heavily as part
[PJC] [1913 Webster]

Word Net



1 the vertical force exerted by a mass as a result of gravity
2 sports equipment used in calisthenic exercises and weightlifting; a weight that is not attached to anything and is raised and lowered by use of the hands and arms [syn: free weight, exercising weight]
3 the relative importance granted to something; "his opinion carries great weight"
4 an artifact that is heavy
5 an oppressive feeling of heavy force; "bowed down by the weight of responsibility"
6 a system of units used to express the weight of something [syn: system of weights]
7 a unit used to measure weight; "he placed two weights in the scale pan" [syn: weight unit]
8 (statistics) a coefficient assigned to elements of a frequency distribution in order to represent their relative importance [syn: weighting]


1 weight down with a load [syn: burden, burthen, weight down] [ant: unburden]
2 present with a bias; "He biased his presentation so as to please the share holders" [syn: slant, angle]

Moby Thesaurus

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wiht, ġewiht




  1. The force on an object due to the gravitational attraction between it and the Earth.
  2. An object used to make something heavier.
  3. A standardized block of metal used in a balance to measure the mass of another object.
  4. : A disc of iron, dumbbell, or barbell used for training the muscles.
  5. Mass (net weight, atomic weight, molecular weight, troy weight, carat weight, etc.).
  6. A variable which multiplies a value for ease of statistical manipulation.
  7. The smallest cardinality of a base.
  8. The boldness of a font; the relative thickness of its strokes.
Compare to mass.


force due to gravity
object to make something heavier
measuring weights
sport device
physics: mass
statistics: statistical value

Related terms


  1. To add weight to something, in order to make it heavier.
  2. To load, burden or oppress someone.
  3. In the context of "transitive|mathematics": To assign weights to individual statistics.
  4. To bias something; to slant.
  5. In the context of "transitive|horse racing": To handicap a horse with a specified weight.


add weight
in mathematics
to bias, to slant
to handicap a horse
In the physical sciences, weight is a measurement of the gravitational force acting on an object.

Weight and mass

In modern scientific usage, weight and mass are fundamentally different quantities: mass is an intrinsic property of matter, whereas weight is a force that results from the action of gravity on matter: it measures how strongly gravity pulls on that matter.
However, the recognition of this difference is, historically, a relatively recent development and in many everyday situations the word "weight" continues to be used when "mass" is meant. For example, we say that an object "weighs one kilogram", even though the kilogram is a unit of mass.
The distinction between mass and weight is unimportant for many practical purposes because the strength of gravity is very simliar everywhere on the surface of the Earth. In such a constant gravitational field, the gravitational force exerted on an object (its weight) is directly proportional to its mass. So, if object A weighs, say, 10 times as much as object B, then object A's mass is 10 times that of object B. This means that an object's mass can be measured indirectly by its weight (for conversion formulas see below). For example, when we buy a bag of sugar we can measure its weight (how hard it presses down on the scales) and be sure that this will give a good indication of the quantity that we are actually interested in, which is the mass of sugar in the bag. Nevertheless, slight variations in the Earth's gravitational field do exist (see Earth's gravity). These alter the relationship between weight and mass, and must be taken into account in high precision weight measurements that are intended to indirectly measure mass.
The use of "weight" for "mass" also persists in some scientific terminology – for example, in the chemical terms "atomic weight", "molecular weight", and "formula weight", rather than the preferred "atomic mass" etc.
The difference between mass and force becomes obvious when:
  • objects are compared in different gravitational fields, such as away from the Earth's surface. For example, on the surface of the Moon, gravity is only about one-sixth as strong as on the surface of the Earth. A one-kilogram mass is still a one-kilogram mass (as mass is an intrinsic property of the object) but the downward force due to gravity is only one-sixth of what the object would experience on Earth.
  • locating the center of gravity of an object (although if the gravitation field is uniform, the center of gravity will coincide with the center of mass).
  • an object is submersed in a fluid (for instance, a brick weighs less when placed in water, and helium balloon in the atmosphere appears to have negative weight).

Units of weight

Systems of units of weight (force) and mass have a tangled history, partly because the distinction was not properly understood when many of the units first came into use.

SI units

In most modern scientific work, physical quantities are measured in SI units. The SI unit of mass (and hence weight in some everyday senses) is the kilogram. The SI unit of force (and hence weight in the mechanics sense) is the newton (N) – which can also be expressed in SI base units as kg·m/s² (kilograms times metres per second squared).
The gravitational force exerted on an object is proportional to the mass of the object, so it is reasonable to think of the strength of gravity as measured in terms of force per unit mass, that is, newtons per kilogram (N/kg). However, the unit N/kg resolves to m/s²; (metres per second per second), which is the SI unit of acceleration, and in practice gravitational strength is usually quoted as an acceleration.

The pound and other non-SI units

In United States customary units, the pound can be either a unit of force or a unit of mass. Related units used in some distinct, separate subsystems of units include the poundal and the slug. The poundal is defined as the force necessary to accelerate a one-pound object at 1 ft/s², and is equivalent to about 1/32 of a pound (force). The slug is defined as the amount of mass that accelerates at 1 ft/s² when a pound of force is exerted on it, and is equivalent to about 32 pounds (mass).
The kilogram-force is a non-SI unit of force, defined as the force exerted by a one-kilogram mass in standard Earth gravity (equal to 9.80665 newtons exactly). The dyne is the cgs unit of force and is not a part of SI, while weights measured in the cgs unit of mass, the gram, remain a part of SI.

Conversion between weight (force) and mass

To convert between weight (force) and mass we use Newton's second law, F = ma (force = mass × acceleration). Here, F is the force (weight) due to gravity, m is the mass of the object in question, and a is the acceleration due to gravity, on Earth approximately 9.8 m/s² or 32.2 ft/s². In this context the same equation is often written as W = mg, with W standing for weight, and g for the acceleration due to gravity.

Sensation of weight

see also apparent weight The weight force that we actually sense is not the downward force of gravity, but the normal force (an upward contact force) exerted by the surface we stand on, which opposes gravity and prevents us falling to the center of the Earth. This normal force, called the apparent weight, is the one that is measured by a spring scale.
For a body supported in a stationary position, the normal force balances the earth's gravitational force, and so apparent weight has the same magnitude as actual weight. (Technically, things are slightly more complicated. For example, an object immersed in water weighs less, according to a spring scale, than the same object in air; this is due to buoyancy, which opposes the weight force and therefore generates a smaller normal. These and other factors are explained further under apparent weight.)
If there is no contact with any surface to provide such an opposing force then there is no sensation of weight (no apparent weight). This happens in free-fall, as experienced by sky-divers (until they approach terminal velocity) and astronauts in orbit, who feel "weightless" even though their bodies are still subject to the force of gravity: they're just no longer resisting it. The experience of having no apparent weight is also known as microgravity.
A degree of reduction of apparent weight occurs, for example, in elevators. In an elevator, a spring scale will register a decrease in a person's (apparent) weight as the elevator starts to accelerate downwards. This is because the opposing force of the elevator's floor decreases as it accelerates away underneath one's feet.

Measuring weight

Main article: Weighing scale
Weight is commonly measured using one of two methods. A spring scale or hydraulic or pneumatic scale measures weight force (strictly apparent weight force) directly. If the intention is to measure mass rather than weight, then this force must be converted to mass. As explained above, this calculation depends on the strength of gravity. Household and other low precision scales that are calibrated in units of mass (such as kilograms) assume roughly that standard gravity will apply. However, although nearly constant, the apparent or actual strength of gravity does in fact vary very slightly in different places on the earth (see standard gravity, physical geodesy, gravity anomaly and gravity). This means that same object (the same mass) will exert a slightly different weight force in different places. High precision spring scales intended to measure mass must therefore be calibrated specifically according their location on earth.
Mass may also be measured with a balance, which compares the item in question to others of known mass. This comparison remains valid whatever the local strength of gravity. If weight force, rather than mass, is required, then this can be calculated by multiplying mass by the acceleration due to gravity – either standard gravity (for everyday work) or the precise local gravity (for precision work).
Gross weight is a term that generally is found in commerce or trade applications, and refers to the gross or total weight of a product and its packaging. Conversely, net weight refers to the intrinsic weight of the product itself, discounting the weight of packaging or other materials.

Relative weights on the Earth, other planets and the Moon

The table below shows comparative gravitational accelerations at the surface of the Sun, the Earth's moon, each of the planets in the solar system, and Pluto. The “surface” is taken to mean the cloud tops of the gas giants (Jupiter, Saturn, Uranus and Neptune). For the Sun, the surface is taken to mean the photosphere. The values in the table have not been de-rated for the centrifugal effect of planet rotation (and cloud-top wind speeds for the gas giants) and therefore, generally speaking, are similar to the actual gravity that would be experienced near the poles.


weight in Afrikaans: Gewig
weight in Arabic: وزن
weight in Asturian: Pesu
weight in Bengali: ওজন (ভার)
weight in Min Nan: Tāng-liōng
weight in Belarusian: Вага
weight in Bosnian: Težina
weight in Bulgarian: Тегло
weight in Catalan: Pes
weight in Czech: Váha
weight in Danish: Vægt (fysik)
weight in German: Gewicht
weight in Estonian: Kaal
weight in Spanish: Peso
weight in Esperanto: Pezo
weight in Basque: Pisu
weight in Persian: وزن
weight in French: Poids
weight in Galician: Peso
weight in Hindi: भार
weight in Korean: 무게
weight in Croatian: Težina
weight in Ido: Pezo
weight in Indonesian: Berat
weight in Icelandic: Þyngd
weight in Italian: Forza peso
weight in Hebrew: משקל (פיזיקה)
weight in Latvian: Svars
weight in Lithuanian: Svoris
weight in Hungarian: Súly
weight in Macedonian: Тежина
weight in Malayalam: ഭാരം
weight in Malay (macrolanguage): Berat
weight in Dutch: Gewicht
weight in Japanese: 重さ
weight in Norwegian: Tyngde
weight in Polish: Ciężar
weight in Portuguese: Peso
weight in Kölsch: Jeweech
weight in Romanian: Greutate
weight in Quechua: Llasaq kay
weight in Russian: Вес
weight in Sicilian: Pisu
weight in Simple English: Weight
weight in Slovak: Gravitačná hmotnosť
weight in Slovenian: Teža
weight in Serbian: Тежина
weight in Finnish: Paino
weight in Swedish: Tyngd
weight in Thai: น้ำหนัก
weight in Vietnamese: Lực hấp dẫn#Tr.E1.BB.8Dng_l.E1.BB.B1c
weight in Turkish: Ağırlık
weight in Ukrainian: Вага
weight in Yiddish: וואג
weight in Chinese: 重量
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