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[is-muh s] /ˈɪs məs/
noun, plural isthmuses, isthmi
[is-mahy] /ˈɪs maɪ/ (Show IPA)
a narrow strip of land, bordered on both sides by water, connecting two larger bodies of land.
Anatomy, Zoology. a connecting, usually narrow, part, organ, or passage, especially when joining structures or cavities larger than itself.
Ichthyology. the narrow fleshy area between the sides of the lower jaw of a fish.
1545-55; < Latin < Greek isthmós neck (of land)
Related forms
isthmoid, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for isthmus
  • The north is separated from the south by the neck, an isthmus of swampland.
British Dictionary definitions for isthmus


noun (pl) -muses, -mi (-maɪ)
a narrow strip of land connecting two relatively large land areas
  1. a narrow band of tissue connecting two larger parts of a structure
  2. a narrow passage connecting two cavities
Derived Forms
isthmoid, adjective
Word Origin
C16: from Latin, from Greek isthmos
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 isthmus

1550s, from Latin isthmus, from Greek isthmos "narrow passage, narrow neck of land," especially that of Corinth, of unknown origin, perhaps from eimi "to go" + suffix -thmo (cf. ithma "a step, movement").

Online Etymology Dictionary, © 2010 Douglas Harper
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isthmus in Medicine

isthmus isth·mus (ĭs'məs)
n. pl. isth·mus·es or isth·mi (-mī')
A constriction or narrow passage connecting two larger parts of an organ or other anatomical structure.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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isthmus in Science
Plural isthmuses or isthmi (ĭs'mī')
A narrow strip of land connecting two larger masses of land.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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isthmus in Culture
isthmus [(is-muhs)]

A narrow strip of land that connects two larger bodies of land and has water on both sides.

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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Encyclopedia Article for isthmus

narrow strip of land connecting two large land areas otherwise separated by the sea. Unquestionably the two most famous are the Isthmus of Panama, connecting North and South America, and the Isthmus of Suez, connecting Africa and Asia. Historically the Isthmus of Corinth was of major importance because it connected what otherwise would be the island of the Peloponnese with the rest of the Greek peninsula. Isthmuses are of great importance in plant and animal geography because they offer a path for the migration of land plants and animals between the two land masses they connect.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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