# Length

Length is a measure of distance.wikipedia
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### Distance

distancesproximitydepth
Length is a measure of distance. In the International System of Quantities, length is a quantity with dimension distance.
In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two counties over").

### International System of Quantities

base quantitiesISQbase quantity
In the International System of Quantities, length is a quantity with dimension distance.
The International System of Quantities (ISQ) is a system based on seven base quantities: length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity.

### System of measurement

Systems of measurementsystem of unitsHistorical weights and measures
In most systems of measurement, the unit of length is a base unit, from which other units are derived.
In most systems, length (distance), mass, and time are base quantities.

### Area

surface areaArea (geometry)area formula
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).
It is the two-dimensional analog of the length of a curve (a one-dimensional concept) or the volume of a solid (a three-dimensional concept).

### Height

tallhhigh
Types of length include height, which is vertical length or vertical extent, and width or breadth, which are the side-to-side length, measuring across the object at right angles to the height.
In elementary models of space, height may indicate the third dimension, the other two being length and width.

### Unit of measurement

unitunits of measurementweights and measures
There are several units that are used to measure length.
For example, a length is a physical quantity.

### Volume

volumetriccapacityOrders of magnitude (volume)
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).
]]Any unit of length gives a corresponding unit of volume: the volume of a cube whose sides have the given length.

### Base unit (measurement)

base unitbase unitsfundamental quantity
In most systems of measurement, the unit of length is a base unit, from which other units are derived.
The traditional fundamental dimensions of physical quantity are mass, length, time, charge, and temperature, but in principle, other fundamental quantities could be used.

### SI base unit

base unitSI base unitsbase units
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 units and their physical quantities are the second for time, the metre for measurement of length, the kilogram for mass, the ampere for electric current, the kelvin for temperature, the mole for amount of substance, and the candela for luminous intensity.

### International System of Units

SISI unitsSI unit
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.

### Centimetre

cmcentimetercentimeters
The centimetre and the kilometre, derived from the metre, are also commonly used units.
A centimetre (international spelling as used by the International Bureau of Weights and Measures; symbol cm) or centimeter (American spelling) is a unit of length in the metric system, equal to one hundredth of a metre, centi being the SI prefix for a factor of 1⁄100.

### Measurement

measuremeasuringmeasurements
There are several units that are used to measure length.

### Inch

ininchesinternational inch
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.
The inch (abbreviation: in or ″) is a unit of length in the (British) imperial and United States customary systems of measurement.

### Foot (unit)

feetftfoot
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.
The foot ( pl. feet; abbreviation: ft; symbol: ′, the prime symbol) is a unit of length in the imperial and US customary systems of measurement.

### Yard

yardsydTotal return yards
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.
The yard (abbreviation: yd) is an English unit of length, in both the British imperial and US customary systems of measurement, that comprises 3 feet or 36 inches.

### Orders of magnitude (length)

mm100 nmGm
The following are examples of orders of magnitude for different lengths.

### Arc length

rectifiable curvearclengthlength
Since it is straightforward to calculate the length of each linear segment (using the Pythagorean theorem in Euclidean space, for example), the total length of the approximation can be found by summing the lengths of each linear segment; that approximation is known as the (cumulative) chordal distance.

### Reciprocal length

cm −1 inverse centimeterinverse length
As the reciprocal of length, common units used for this measurement include the reciprocal metre or inverse metre (symbol: m −1 ), the reciprocal centimetre or inverse centimetre (symbol: cm −1 ), and, in optics, the dioptre.

### Metre

metermmetres
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 metre (Commonwealth spelling and BIPM spelling ) or meter (American spelling ) (from the French unit mètre, from the Greek noun μέτρον, "measure") is the base unit of length in the International System of Units (SI).

### Kilometre

kmkilometerkilometers
The centimetre and the kilometre, derived from the metre, are also commonly used units.

### Astronomical unit

AUastronomical unitsAUs
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.

### Metric system

metricmetric unitsmetric unit

### Parsec

Mpcpckpc
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.

### Quantity

quantitiesquantitativeamount
In the International System of Quantities, length is a quantity with dimension distance.

### Dimension

dimensionsdimensionalone-dimensional
Length is commonly understood to mean the most extended dimension of an object.