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[rahy-buh-sohm] /ˈraɪ bəˌsoʊm/
noun, Cell Biology
a tiny, somewhat mitten-shaped organelle occurring in great numbers in the cell cytoplasm either freely, in small clusters, or attached to the outer surfaces of endoplasmic reticula, and functioning as the site of protein manufacture.
Origin of ribosome
1955-60; ribo(se) + -some3
Related forms
ribosomal, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for ribosome
  • Despite the fact that both chloramphenicol and doxycycline target the ribosome, no mutation to the ribosome was seen.
  • The ribosome mediates the formation of a polypeptide sequence based on the mrna sequence.
  • The ribosome translates a single protein from the viral genome.
British Dictionary definitions for ribosome


any of numerous minute particles in the cytoplasm of cells, either free or attached to the endoplasmic reticulum, that contain RNA and protein and are the site of protein synthesis
Derived Forms
ribosomal, adjective
Word Origin
C20: from ribo(nucleic acid) + -some³
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 ribosome

1958, coined by U.S. microbiologist Richard B. Roberts (1910-1980) from ribo(nucleic acid) + -some "body."

Online Etymology Dictionary, © 2010 Douglas Harper
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ribosome in Medicine

ribosome ri·bo·some (rī'bə-sōm')
A minute round cytoplasmic particle composed of RNA and protein that is the site of protein synthesis as directed by mRNA.

ri'bo·so'mal (-sō'məl) adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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ribosome in Science
A sphere-shaped structure within the cytoplasm of a cell that is composed of RNA and protein and is the site of protein synthesis. Ribosomes are free in the cytoplasm and often attached to the membrane of the endoplasmic reticulum. Ribosomes exist in both eukaryotic and prokaryotic cells. Plastids and mitochondria in eukaryotic cells have smaller ribosomes similar to those of prokaryotes. See more at cell.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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ribosome in Culture
ribosome [(reye-buh-sohm)]

A small, ball-like structure in the cell, made of proteins and RNA molecules, that serves as a platform on which the cell's proteins are made.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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