[ noo-klee-uh-luh s, nyoo- ]
/ nuˈkli ə ləs, nyu- /

noun, plural nu·cle·o·li [noo-klee-uh-lahy, nyoo-] /nuˈkli əˌlaɪ, nyu-/. Cell Biology.

a conspicuous, rounded body within the nucleus of a cell.

Origin of nucleolus

1835–45; < Late Latin: small kernel, equivalent to nucle(us) kernel (see nucleus) + -olus -ole1 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for nucleoli

British Dictionary definitions for nucleoli


/ (ˌnjuːklɪˈəʊləs) /

noun plural -li (-laɪ)

a small rounded body within a resting nucleus that contains RNA and proteins and is involved in the production of ribosomesAlso called: nucleole

Derived Forms

nucleolar, nucleolate or nucleolated, adjective

Word Origin for nucleolus

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

Medicine definitions for nucleoli


[ nōō-klēə-ləs ]

n. pl. nu•cle•o•li (-lī′)

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.

Related forms

nu•cleo•lar (-lər) adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for nucleoli


[ nōō-klēə-ləs ]

Plural nucleoli (nōō-klēə-lī′)

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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.