Nanometre

# Nanometre

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A nanometre is a unit
Units of measurement
A unit of measurement is a definite magnitude of a physical quantity, defined and adopted by convention and/or by law, that is used as a standard for measurement of the same physical quantity. Any other value of the physical quantity can be expressed as a simple multiple of the unit of...

of length
Length
In geometric measurements, length most commonly refers to the longest dimension of an object.In certain contexts, the term "length" is reserved for a certain dimension of an object along which the length is measured. For example it is possible to cut a length of a wire which is shorter than wire...

in the metric system
Metric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...

, equal to one billion
Billion
Billion may refer to: In numbers:*Long and short scales**1,000,000,000 , one thousand million, 109, in the short scale**1,000,000,000,000 , one million million, 1012, in the long scaleIn other usage:...

th of a metre
Metre
The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...

. The name combines the SI prefix
SI prefix
The International System of Units specifies a set of unit prefixes known as SI prefixes or metric prefixes. An SI prefix is a name that precedes a basic unit of measure to indicate a decadic multiple or fraction of the unit. Each prefix has a unique symbol that is prepended to the unit symbol...

nano- (from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

, , "dwarf") with the parent unit name metre (from Greek , , "unit of measurement").

The nanometre is often used to express dimensions on the atomic scale: the diameter of a helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

atom, for example, is about 0.1 nm, and that of a ribosome
Ribosome
A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....

is about 20 nm. The nanometre is commonly used to specify the wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...

Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...

near the visible part of the spectrum
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....

: visible light, in particular, ranges from 400 to 700 nm. In these uses, the nanometre appears to be supplanting the other common unit for atomic scale dimensions, the angstrom
Ångström
The angstrom or ångström, is a unit of length equal to 1/10,000,000,000 of a meter . Its symbol is the Swedish letter Å....

, which is equal to 0.1 nanometre.

This unit is often associated with the field of nanotechnology
Nanotechnology
Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres...

. Since late 1980s, it has also been used to describe generations of the manufacturing technology in the semiconductor industry
Semiconductor industry
The semiconductor industry is the aggregate collection of companies engaged in the design and fabrication of semiconductor devices. It formed around 1960, once the fabrication of semiconductors became a viable business...

.

The nanometre was formerly known as the millimicron, since it is 1/1000 of a micron
Micron
Micron can refer to:*Micron, a non-SI name for micrometre*Micron , is the measurement used to express the diameter of a wool fibre.*A small curved diacritic mark above some letters, used to indicate shortness, e.g...

(micrometre), and was often denoted by the symbol or (more rarely) µµ.

One nanometre is one billionth (1/1000000000) of a metre.