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Longman Dictionary of Contemporary English
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The Collaborative International Dictionary

nano- \nan"o-\ (n[a^]n"[-o]-), pref.

  1. A prefix meaning one-billionth; as, a nanogram is one-thousandth of a microgram.

  2. Very small; submicroscopic; -- used to designate sizes smaller than those that would be referred to as micro-; as, nanoscale manipulations.

Douglas Harper's Etymology Dictionary

introduced 1947 (at 14th conference of the Union Internationale de Chimie) as a prefix for units of one thousand-millionth part, from Greek nanos "a dwarf." According to Watkins, this is originally "little old man," from nannos "uncle," masc. of nanna "aunt" (see nana). Earlier it was used as a prefix to mean "dwarf, dwarfish," and still in a non-scientific sense of "very small."


pre. 1 In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 10−9. Symbol: n 2 Derived from the nanotechnology industry


Nano- (symbol n) is a unit prefix meaning one billionth. Used primarily with the metric system, this prefix denotes a factor of 10 or . It is frequently encountered in science and electronics for prefixing units of time and length.


  • One nanometer is about the length that a fingernail grows in one second.
  • Three gold atoms lined up are about one nanometer long.
  • If a toy marble were scaled down to one nanometer wide, Earth would scale to about one meter (3.3 feet) wide.
  • One nanosecond is about the time required for light to travel 30 cm in air, or 20 cm in an optical fiber.

The prefix is derived from the Greek (Latin nanus), meaning "dwarf", and was officially confirmed as standard in 1960.

When used as a prefix for something other than a unit of measure (as in "nanoscience"), nano refers to nanotechnology, or on a scale of nanometres. See nanoscopic scale.