• synonyms


[noo-klee-uh-luh s, nyoo-]
noun, plural nu·cle·o·li [noo-klee-uh-lahy, nyoo-] /nuˈkli əˌlaɪ, nyu-/. Cell Biology.
  1. a conspicuous, rounded body within the nucleus of a cell.
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Origin of nucleolus

1835–45; < Late Latin: small kernel, equivalent to nucle(us) kernel (see nucleus) + -olus -ole1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for nucleoli

Historical Examples

  • Highly refracting points or nucleoli were visible in their anterior.


    T. Spencer Cobbold

  • Within the nucleus are often to be found one or two nucleoli with a relatively thick and deeply stained membrane.

  • The above mode of increase for the nucleoli appears to be exceptional.

  • The aberrant bodies in these figures are probably remains of the nucleoli; they are found only in iron-hæmatoxylin preparations.

  • Partial rest stage between first and second maturation divisions, two nucleoli present.

British Dictionary definitions for nucleoli


noun plural -li (-laɪ)
  1. a small rounded body within a resting nucleus that contains RNA and proteins and is involved in the production of ribosomesAlso called: nucleole
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Derived Formsnucleolar, nucleolate or nucleolated, adjective

Word Origin

C19: from Latin, diminutive of nucleus
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

Word Origin and History for nucleoli



1845, from Latin nucleolus, literally "a little nut," diminutive of nucleus (see nucleus).

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Online Etymology Dictionary, © 2010 Douglas Harper

nucleoli in Medicine


n. pl. nu•cle•o•li (-lī′)
  1. A small, typically round granular body composed of protein and RNA in the nucleus of a cell, usually associated with a specific chromosomal site and involved in ribosomal RNA synthesis and the formation of ribosomes.
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Related formsnu•cleo•lar (-lər) adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

nucleoli in Science


Plural nucleoli (nōō-klēə-lī′)
  1. A small, typically spherical granular body located in the nucleus of a eukaryotic cell, composed largely of protein and RNA. When the cell is not undergoing division, loops of DNA from one or more chromosomes extend into the nucleolus and direct the synthesis of ribosomal RNA and the formation of ribosomes. The ribosomes are eventually transferred out of the nucleus via pores in the nuclear envelope into the cytoplasm.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.