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[sil-ee-uh m] /ˈsɪl i əm/
singular of cilia.
Origin of cilium
From Latin


[sil-ee-uh] /ˈsɪl i ə/
plural noun, singular cilium
[sil-ee-uh m] /ˈsɪl i əm/ (Show IPA)
Biology. minute hairlike organelles, identical in structure to flagella, that line the surfaces of certain cells and beat in rhythmic waves, providing locomotion to ciliate protozoans and moving liquids along internal epithelial tissue in animals.
Anatomy. the eyelashes.
1705-15; New Latin, plural of cilium eyelash, Latin: upper eyelid, perhaps a back formation from supercilium eyebrow; see supercilium Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for cilium


noun (pl) cilia (ˈsɪlɪə)
any of the short thread-like projections on the surface of a cell, organism, etc, whose rhythmic beating causes movement of the organism or of the surrounding fluid
the technical name for eyelash
Word Origin
C18: New Latin, from Latin: (lower) eyelid, eyelash


the plural of cilium
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Word Origin and History for cilium



1715, from Latin cilia, plural of cilium "eyelid, eyelash," perhaps related to celare "to cover, hide," from PIE root *kel- "to conceal" (see cell), but words for this part of the face can be tricky (see brow). It sometimes is pluralized in English, which is an error. Related: Ciliated; ciliary; ciliate.

Online Etymology Dictionary, © 2010 Douglas Harper
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cilium in Medicine

cilium cil·i·um (sĭl'ē-əm)
n. pl. cil·i·a (-ē-ə)

  1. See eyelash.

  2. A microscopic hairlike process extending from the surface of a cell or unicellular organism, capable of rhythmical motion, and acting with other such structures to cause the movement of the cell or of the surrounding medium.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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cilium in Science
Plural cilia
A tiny hairlike projection on the surface of some cells and microscopic organisms, especially protozoans. Cilia are capable of whipping motions and are used by some microorganisms, such as paramecia, for movement. Cilia lining the human respiratory tract act to remove foreign matter from air before it reaches the lungs.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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