AskDefine | Define distance

Dictionary Definition

distance

Noun

1 the property created by the space between two objects or points
2 a distant region; "I could see it in the distance"
3 size of the gap between two places; "the distance from New York to Chicago"; "he determined the length of the shortest line segment joining the two points" [syn: length]
4 indifference by personal withdrawal; "emotional distance" [syn: aloofness]
5 the interval between two times; "the distance from birth to death"; "it all happened in the space of 10 minutes" [syn: space]
6 a remote point in time; "if that happens it will be at some distance in the future"; "at a distance of ten years he had forgotten many of the details"

Verb

1 keep at a distance; "we have to distance ourselves from these events in order to continue living"
2 go far ahead of; "He outdistanced the other runners" [syn: outdistance, outstrip]

User Contributed Dictionary

English

Pronunciation

  • /ˈdɪstəns/

Noun

  1. The amount of space between two points, usually geographical points, usually (but not necessarily) measured along a straight line.
    The distance to Petersborough is thirty miles.
  2. In the context of "uncountable|figurative": The entire amount of space to the objective.
    He had promised to perform this task, but did not go the distance.
  3. In the context of "uncountable|figurative": A considerable amount of space.
    The friendship did not survive the row: they kept each other at a distance.

Related terms

Translations

amount of space between two points
  • Breton: pellder -ioù p
  • Catalan: distància
  • Czech: vzdálenost
  • Dutch: afstand
  • Esperanto: distanco
  • Finnish: etäisyys
  • French: distance
  • German: Distanz, Entfernung, Abstand
  • Hebrew: מרחק
  • Indonesian: jarak
  • Interlingua: distantia
  • Italian: distanza
  • Japanese: 距離
  • Korean: 거리 [距離] (geori)
  • Lithuanian: nuotolis, atstumas, sometimes distancija
  • Malayalam: ദൂരം (dooram), അകലം (akalam)
  • Polish: odległość, droga, dystans
  • Portuguese: distância
  • Romanian: distanţă
  • Slovene: razdalja (1)
  • Spanish: distancia
  • Swedish: avstånd, distans
  • Telugu: దూరము

See also

Verb

  1. To move away from someone or something.

Translations

move away

French

Pronunciation

  • /dis'tɔ̃s(ə)/

Noun

fr-noun f

Derived terms

Extensive Definition

Distance is a numerical description of how far apart objects are. In physics or everyday discussion, distance may refer to a physical length, a period of time, or an estimation based on other criteria (e.g. "two counties over"). In mathematics, distance must meet more rigorous criteria.
In most cases there is symmetry and "distance from A to B" is interchangeable with "distance between B and A".

Mathematics

Geometry

In neutral geometry, the minimum distance between two points is the length of the line segment between them.
In analytic geometry, the distance between two points of the xy-plane can be found using the distance formula. The distance between (x1, y1) and (x2, y2) is given by
d=\sqrt=\sqrt.\,
Similarly, given points (x1, y1, z1) and (x2, y2, z2) in three-space, the distance between them is
d=\sqrt=\sqrt.
Which is easily proven by constructing a right triangle with a leg on the hypotenuse of another (with the other leg orthogonal to the plane that contains the 1st triangle) and applying the Pythagorean theorem.
In the study of complicated geometries, we call this (most common) type of distance Euclidean distance, as it is derived from the Pythagorean theorem, which does not hold in Non-Euclidean geometries. This distance formula can also be expanded into the arc-length formula.

Distance in Euclidean space

In the Euclidean space Rn, the distance between two points is usually given by the Euclidean distance (2-norm distance). Other distances, based on other norms, are sometimes used instead.
For a point (x1, x2, ...,xn) and a point (y1, y2, ...,yn), the Minkowski distance of order p (p-norm distance) is defined as: p need not be an integer, but it cannot be less than 1, because otherwise the triangle inequality does not hold.
The 2-norm distance is the Euclidean distance, a generalization of the Pythagorean theorem to more than two coordinates. It is what would be obtained if the distance between two points were measured with a ruler: the "intuitive" idea of distance.
The 1-norm distance is more colourfully called the taxicab norm or Manhattan distance, because it is the distance a car would drive in a city laid out in square blocks (if there are no one-way streets).
The infinity norm distance is also called Chebyshev distance. In 2D it represents the distance kings must travel between two squares on a chessboard.
The p-norm is rarely used for values of p other than 1, 2, and infinity, but see; super ellipse.
In physical space the Euclidean distance is in a way the most natural one, because in this case the length of a rigid body does not change with rotation.

General case

In mathematics, in particular geometry, a distance function on a given set M is a function d: M×M → R, where R denotes the set of real numbers, that satisfies the following conditions:
  • d(x,y) ≥ 0, and d(x,y) = 0 if and only if x = y. (Distance is positive between two different points, and is zero precisely from a point to itself.)
  • It is symmetric: d(x,y) = d(y,x). (The distance between x and y is the same in either direction.)
  • It satisfies the triangle inequality: d(x,z) ≤ d(x,y) + d(y,z). (The distance between two points is the shortest distance along any path).
Such a distance function is known as a metric. Together with the set, it makes up a metric space.
For example, the usual definition of distance between two real numbers x and y is: d(x,y) = |x − y|. This definition satisfies the three conditions above, and corresponds to the standard topology of the real line. But distance on a given set is a definitional choice. Another possible choice is to define: d(x,y) = 0 if x = y, and 1 otherwise. This also defines a metric, but gives a completely different topology, the "discrete topology"; with this definition numbers cannot be arbitrarily close.

Distances between sets and between a point and a set

Various distance definitions are possible between objects. For example, between celestial bodies one should not confuse the surface-to-surface distance and the center-to-center distance. If the former is much less than the latter, as for a LEO, the first tends to be quoted (altitude), otherwise, e.g. for the Earth-Moon distance, the latter.
There are two common definitions for the distance between two non-empty subsets of a given set:
  • One version of distance between two non-empty sets is the infimum of the distances between any two of their respective points, which is the every-day meaning of the word. This is a symmetric prametric. On a collection of sets of which some touch or overlap each other, it is not "separating", because the distance between two different but touching or overlapping sets is zero. Also it is not hemimetric, i.e., the triangle inequality does not hold, except in special cases. Therefore only in special cases this distance makes a collection of sets a metric space.
  • The Hausdorff distance is the larger of two values, one being the supremum, for a point ranging over one set, of the infimum, for a second point ranging over the other set, of the distance between the points, and the other value being likewise defined but with the roles of the two sets swapped. This distance makes the set of non-empty compact subsets of a metric space itself a metric space.
The is the infimum of the distances between the point and those in the set. This corresponds to the distance, according to the first-mentioned definition above of the distance between sets, from the set containing only this point to the other set.
In terms of this, the definition of the Hausdorff distance can be simplified: it is the larger of two values, one being the supremum, for a point ranging over one set, of the distance between the point and the set, and the other value being likewise defined but with the roles of the two sets swapped.

Distance versus displacement

Distance cannot be negative. Distance is a scalar quantity, containing only a magnitude, whereas displacement is an equivalent vector quantity containing both magnitude and direction.
The distance covered by a vehicle (often recorded by an odometer), person, animal, object, etc. should be distinguished from the distance from starting point to end point, even if latter is taken to mean e.g. the shortest distance along the road, because a detour could be made, and the end point can even coincide with the starting point.

See also

References

  • E. Deza, M.M. Deza, Dictionary of Distances, Elsevier (2006) ISBN 0-444-52087-2
distance in Arabic: مسافة
distance in Bulgarian: Разстояние
distance in Catalan: Distància
distance in Czech: Vzdálenost
distance in Danish: Distance
distance in German: Abstand
distance in Modern Greek (1453-): Απόσταση
distance in Spanish: Distancia
distance in Esperanto: Distanco
distance in Basque: Luzera
distance in French: Distance (mathématiques)
distance in Galician: Distancia
distance in Korean: 거리
distance in Ido: Disto
distance in Indonesian: Jarak
distance in Interlingua (International Auxiliary Language Association): Distantia
distance in Icelandic: Fjarlægðarformúlan
distance in Italian: Distanza
distance in Luxembourgish: Ofstand
distance in Malay (macrolanguage): Jarak
distance in Dutch: Afstand
distance in Japanese: 距離
distance in Polish: Odległość
distance in Portuguese: Distância
distance in Russian: Расстояние
distance in Simple English: Distance
distance in Slovak: Vzdialenosť
distance in Slovenian: Razdalja
distance in Swedish: Avstånd
distance in Thai: ระยะทาง
distance in Vietnamese: Khoảng cách
distance in Urdu: فاصلہ (ریاضی)
distance in Yiddish: ווייטקייט
distance in Chinese: 距离
distance in Finnish: Välimatka

Synonyms, Antonyms and Related Words

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