AskDefine | Define length

Dictionary Definition



1 the linear extent in space from one end to the other; the longest horizontal dimension of something that is fixed in place; "the length of the table was 5 feet"
2 continuance in time; "the ceremony was of short duration"; "he complained about the length of time required" [syn: duration]
3 the property of being the extent of something from beginning to end; "the editor limited the length of my article to 500 words"
4 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: distance]
5 a section of something that is long and narrow; "a length of timber"; "a length of tubing"

User Contributed Dictionary





  • , /lɛŋθ/, /lENT/


  1. The measurement of distance along the longest dimension of an object.
    • Robert Frost
      Happiness makes up in height for what it lacks in length.
  2. In the context of "horse racing": The length of a horse, used to indicate the distance between horses at the end of a race.
  3. Magnitude. gloss English
  4. The distance down the pitch that the ball bounces on its way to the batsman.


measurement of distance
length of a horse

Extensive Definition

Length is the long dimension of any object. 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.
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, length is a fundamental unit, from which other units are derived.

Units of length

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 metre and is now defined in terms of the speed of light. The centimetre and the kilometre, derived from the metre, 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

In the context of "section": 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. In this case we define its moving length as the distance between its two endpoints at a given instance.
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))\,
\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.
Since in special relativity the relation of simultaneity depends on the chosen frame of reference, the length of moving rods also depends.

See also

length in Arabic: طول
length in Min Nan: Tn̂g-té
length in Catalan: Longitud (física)
length in Czech: Délka
length in Welsh: Hyd
length in Danish: Længde
length in German: Längenmaß
length in Modern Greek (1453-): Μήκος
length in Esperanto: Longo
length in French: Longueur
length in Korean: 길이
length in Croatian: Duljina
length in Interlingua (International Auxiliary Language Association): Longitude
length in Icelandic: Lengd
length in Italian: Lunghezza
length in Hebrew: אורך
length in Latin: Longitudo
length in Latvian: Garums
length in Hungarian: Hossz
length in Malay (macrolanguage): Panjang
length in Dutch: Lengte (meetkunde)
length in Japanese: 長さ
length in Norwegian: Lengde
length in Portuguese: Comprimento
length in Romanian: Lungime
length in Quechua: Karu kay
length in Russian: Длина
length in Albanian: Gjatësia
length in Simple English: Length
length in Slovenian: Dolžina
length in Serbian: Дужина
length in Finnish: Pituus
length in Swedish: Längd
length in Tamil: நீளம்
length in Thai: มาตราวัดความยาว
length in Vietnamese: Chiều dài
length in Turkish: Uzunluk birimleri
length in Ukrainian: Довжина
length in Yiddish: לענג
length in Chinese: 长度

Synonyms, Antonyms and Related Words

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