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length

 
Dictionary: length   (lĕngkth, lĕngth, lĕnth) pronunciation
n.
  1. The state, quality, or fact of being long. See Usage Note at strength.
  2. The measurement of the extent of something along its greatest dimension: the length of the boat.
  3. A piece, often of a standard size, that is normally measured along its greatest dimension: a length of cloth.
  4. A measure used as a unit to estimate distances: won the race by a length.
  5. Extent or distance from beginning to end: the length of a novel; the length of a journey.
  6. The amount of time between specified moments; the duration: the length of a meeting.
  7. Extent or degree to which an action or policy is carried. Often used in the plural: went to great lengths to prove his point.
  8. Linguistics.
    1. The duration of a vowel.
    2. The duration of a syllable.
  9. The vertical extent of a garment. Often used in combination: knee-length; floor-length.
idiom:

at length

  1. After some time; eventually: At length we arrived at our destination.
  2. For a considerable time; fully: spoke at length about the court ruling.

[Middle English, from Old English lengthu.]


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A one-dimensional extension in space. Length is one of the three fundamental physical quantities, the others being mass and time. It can be measured by comparison with an arbitrary standard; the specific one in most common usage is the international meter. In 1983, at the meeting of the Conférence Général des Poids et Mésures, the meter was redefined in terms of time and the speed of light: “The meter is the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second.” This definition defines the speed of light to be exactly 299 792 458 m/s, and defines the meter in terms of the most accurately known quantity, the second. See also Light; Mass.


Thesaurus: length
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noun

  1. The measure of how far or long something goes in space, time, or degree: extent, reach, span, stretch. See big/small/amount.
  2. An extent, measured or unmeasured, of linear space: distance, space, stretch. Informal piece, way. See big/small/amount.
  3. The ultimate point to which an action, thought, discussion, or policy is carried: end, extreme, limit. See limited/unlimited.

Antonyms: length
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n

Definition: extent of object, distance, time
Antonyms: brevity, conciseness, height


Dental Dictionary: length
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n

The longest measure of an object, or the measurement between the two ends.

A linear measurement of an object, end-to-end; it is usually the longest dimension. The SI unit of length is the metre.

An expression of the longest dimension of an object, or of the measurement between its two ends.

  • crown–heel l. — the distance from the crown of the head to the heel in embryos, fetuses and neonates.
  • crown–rump l. — the distance from the crown of the head to the point of attachment of the tail.
Word Tutor: length
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pronunciation

IN BRIEF: A section of something that is long and narrow. Also: The extent of something from beginning to end.

pronunciation The length of your education is less important than its breadth, and the length of your life is less important than its depth. — Marilyn vos Savant

Wikipedia: Length
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A cuboid demonstrating the dimensions length, width, and height

Length is the long dimension of any object. Not to be confused with Depth which is the property of the object that appears to go away from the observer. The length of a thing is the distance between its ends, its linear extent as measured from end to end. This may be distinguished from height, which is vertical extent, and width or breadth, which are the distance from side to side, measuring across the object at right angles to the length. In the physical sciences and engineering, the word "length" is typically used synonymously with "distance", with symbol l or L or letter-like symbol .

Length is a measure of one dimension, whereas area is a measure of two dimensions (length squared) and volume is a measure of three dimensions (length cubed). In most systems of measurement, the unit of length is a fundamental unit, from which other units are defined.

Contents

History

[1] Measurement has been important ever since man settled from his nomadic lifestyle and started using building materials; occupying land and trading with his neighbours. As society has become more technologically orientated much higher accuracies of measurement are required in an increasingly diverse set of fields, from micro-electronics to interplanetary ranging.

One of the oldest units of length measurement used in the ancient world was the 'cubit' which was the length of the arm from the tip of the finger to the elbow. This could then be subdivided into shorter units like the foot, hand (which at 4 inches is still used today for expressing the height of horses) or finger, or added together to make longer units like the stride. The cubit could vary considerably due to the different sizes of people. As early as the middle of the tenth century it is believed that the Saxon king Edgar kept a "yardstick" at Winchester as the official standard of measurement. A traditional tale tells the story of Henry I (1100-1135) who decreed that the yard should be "the distance from the tip of the King's nose to the end of his outstretched thumb".

Units

In the physical sciences and engineering, when one speaks of "units of length", the word "length" is synonymous with "distance". There are several units that are used to measure length. Units of length may be based on lengths of human body parts, the distance travelled in a number of paces, the distance between landmarks or places on the Earth, or arbitrarily on the length of some fixed object.

In the International System of Units (SI), the basic unit of length is the meter and is now defined in terms of the speed of light. The centimeter and the kilometer, derived from the meter, are also commonly used units. In U.S. customary units, English or Imperial system of units, commonly used units of length are the inch, the foot, the yard, and the mile.

Units used to denote distances in the vastness of space, as in astronomy, are much longer than those typically used on Earth and include the astronomical unit, the light-year, and the parsec.

Units used to denote microscopically small distances, as in chemistry, include the micron and the ångström.

Length of moving rods

While the length of a resting rod can be measured by direct comparison with a measuring rod, this comparison cannot be performed while the rod is moving, due to relativistic concerns. In this case we define its moving length as the distance between its two endpoints at a given instance.

The distance travelled by light in vacuum in 1/299792458 seconds is the standard length

If the world lines of the two endpoints of the rod expressed in the coordinates of an  R \, inertial reference frame are

\mathbf x_1(t) = (t,x_1(t),y_1(t),z_1(t))\,

and

\mathbf x_2(t) = (t,x_2(t),y_2(t),z_2(t)),\,

then the length of the rod in this reference frame at the t \, instance is

l_R(t) = \sqrt{ \left(x_2(t)-x_1(t)\right)^2 + \left(y_2(t)-y_1(t)\right)^2 + \left(z_2(t)-z_1(t)\right)^2 }.

Since in special relativity the relation of simultaneity depends on the chosen frame of reference, the length of moving rods also depends.

Generalizations

In the differential geometry of curves and differential geometry of surfaces, length is an important global Riemannian invariant.

See also


Misspellings: length
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Common misspelling(s) of length

  • lenght

Translations: Length
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Dansk (Danish)
n. - længde, varighed, strækning, stykke

idioms:

  • at length    langt om længe, udførligt arbejde, længe
  • go to great lengths    strække sig meget langt, strække sig vidt
  • length of time    så længe det skal være

Nederlands (Dutch)
lengte, afstand, bepaald/lang stuk, tijdsduur, traject

Français (French)
n. - longueur, long, durée, métrage, morceau, tronçon

idioms:

  • at length    longuement, finalement
  • go to great lengths    se donner énormément de mal (pour faire qch)
  • length of time    intervalle de temps, beaucoup de temps, temps infini

Deutsch (German)
n. - Länge, Stück

idioms:

  • at length    lange, ausführlich, schließlich
  • go to great lengths    alles mögliche tun
  • length of time    (Zeit)länge

Ελληνική (Greek)
n. - μήκος, μάκρος, (χρονική) διάρκεια, μάκρος, κομμάτι (για ύφασμα)

idioms:

  • at length    διεξοδικώς, εν εκτάσει
  • go to great lengths    φτάνω στα άκρα
  • length of time    χρονική διάρκεια

Italiano (Italian)
lunghezza, durata

idioms:

  • at length    dettagliatamente
  • go to great length    darsi da fare per

Português (Portuguese)
n. - comprimento, extensão, duração

idioms:

  • at length    por fim
  • go to great length    esforçar-se
  • length of time    período de tempo

Русский (Russian)
длина, расстояние, продолжительность, отрезок

idioms:

  • at length    подробно, в конце концов
  • go to great length    не останавливаться ни перед чем
  • length of time    отрезок времени

Español (Spanish)
n. - largo, longitud, duración, espacio, extensión, corte, tramo

idioms:

  • at length    por fin, finalmente, con todo detalle
  • go to great lengths    hacer un gran esfuerzo, estar preparado para hacer cualquier cosa
  • length of time    lapso

Svenska (Swedish)
n. - längd, varaktighet, långvarighet, sträcka, utsträckning, (kricket) avstånd till bollens nedslag, rätt avstånd

中文(简体)(Chinese (Simplified))
长度, 全长, 长短, 期间, 全程

idioms:

  • at length    最后, 详细地
  • go to great lengths    竭尽全力
  • length of time    一段时间, 时间, 期间

中文(繁體)(Chinese (Traditional))
n. - 長度, 全長, 長短, 期間, 全程

idioms:

  • at length    最後, 詳細地
  • go to great lengths    竭盡全力
  • length of time    一段時間, 時間, 期間

한국어 (Korean)
n. - 길이, 키, 기간 , 거리

idioms:

  • at length    충분히, 드디어
  • go to great lengths    무슨 짓이라도 하다, 노고를 아끼지 않다

日本語 (Japanese)
n. - 長さ, 期間, 一馬身, 一艇身, 単位となる長さ, 距離

idioms:

  • at arm's length    腕を伸ばした距離に, 少し離れて
  • at length    十分に, ついに, 詳細に, くどくどと
  • length of time    時間

العربيه (Arabic)
‏(الاسم) طول, مدة, مسافه, حد, امتداد‏

עברית (Hebrew)
n. - ‮אורך, תקופה, משך-זמן, חתיכת חבל, חתיכה, אורך הסירה‬


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