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[ep-uh-thee-lee-uh m] /ˌɛp əˈθi li əm/
noun, plural epitheliums, epithelia
[ep-uh-thee-lee-uh] /ˌɛp əˈθi li ə/ (Show IPA).
any animal tissue that covers a surface, or lines a cavity or the like, and that, in addition, performs any of various secretory, transporting, or regulatory functions.
Origin of epithelium
1740-50; < New Latin < Greek epi- epi- + thēl(ḗ) teat + New Latin -ium -ium
Related forms
epithelial, adjective
interepithelial, adjective
nonepithelial, adjective
subepithelial, adjective
unepithelial, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for epithelia


noun (pl) -liums, -lia (-lɪə)
an animal tissue consisting of one or more layers of closely packed cells covering the external and internal surfaces of the body. The cells vary in structure according to their function, which may be protective, secretory, or absorptive
Derived Forms
epithelial, adjective
Word Origin
C18: New Latin, from epi- + Greek thēlē nipple
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 epithelia



1748, Modern Latin (Frederick Ruysch), from Greek epi "upon" (see epi-) + thele "teat, nipple" (see fecund). Related: Epithelial.

Online Etymology Dictionary, © 2010 Douglas Harper
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epithelia in Medicine

epithelium ep·i·the·li·um (ěp'ə-thē'lē-əm)
n. pl. ep·i·the·li·ums or ep·i·the·li·a (-lē-ə)
Membranous tissue composed of one or more layers of cells separated by very little intercellular substance and forming the covering of most internal and external surfaces of the body and its organs.

ep'i·the'li·al 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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epithelia in Science
Plural epithelia
The thin, membranous tissue that lines most of the internal and external surfaces of an animal's body. Epithelium is composed of one or more layers of densely packed cells. In vertebrates, it lines the outer layer of the skin (epidermis), the surface of most body cavities, and the lumen of fluid-filled organs, such as the gut or intestine.

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