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a combining form with the meaning “very small, minute,” used in the formation of compound words (nanoplankton); in the names of units of measure it has the specific sense “one billionth” (10 -9):
nanomole; nanosecond.
Also, nanno-; especially before a vowel, nan-.
Origin of nano-
combining form representing Greek nânos, nánnos dwarf Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for nanno


combining form
denoting 10–9: nanosecond, n
indicating extreme smallness: nanoplankton
Word Origin
from Latin nānus dwarf, from Greek nanos
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for nanno


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."

Online Etymology Dictionary, © 2010 Douglas Harper
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nanno in Medicine

nano- pref.

  1. Extremely small: nanoid.

  2. One-billionth (10-9): nanometer.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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nanno in Science
  1. A prefix that means:

  2. Very small or at a microscopic level, as in nanotube. In this sense, this prefix is sometimes spelled nanno-, as in nannoplankton.

  3. One billionth, as in nanosecond, one billionth of a second.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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