isthmus

American  

[is-muhs] / ˈɪs məs /

noun

isthmuses, plural isthmi plural

1. a narrow strip of land, bordered on both sides by water, connecting two larger bodies of land.

2. Anatomy, Zoology. a connecting, usually narrow, part, organ, or passage, especially when joining structures or cavities larger than itself.

3. Ichthyology. the narrow fleshy area between the sides of the lower jaw of a fish.

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isthmus British  

/ ˈɪsməs /

noun

1. a narrow strip of land connecting two relatively large land areas

2. anatomy

   1. a narrow band of tissue connecting two larger parts of a structure

   2. a narrow passage connecting two cavities

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isthmus Scientific  

/ ĭs′məs /

isthmuses plural

1. A narrow strip of land connecting two larger masses of land.

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isthmus Cultural  

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

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Other Word Forms

• isthmoid
  adjective

Etymology

Origin of isthmus

1545–55; < Latin < Greek isthmós neck (of land)

Explanation

An isthmus is a land bridge, a narrow strip of land that stretches across a body of water to connect two larger land masses. The Greek isthmos means "neck," so you can see how isthmus came to mean the connecting strip between land masses. If you look at an example, say the Isthmus of Panama, you can see how that neck-like bit of land separates the Caribbean Sea from the North Pacific Ocean as it connects North and South America. Think of an isthmus as kind of like a turkey neck that connects the bird's body and head (at least until Thanksgiving).

Example Sentences

Designed to modernise the rail link across the Isthmus of Tehuantepec, the Mexican government has sought to develop the area into a strategic trade corridor, expanding ports, railways and industrial infrastructure.

From BBC • Dec. 28, 2025

And then further, ultimately eradicating screwworm from the Americas north of the Isthmus of Panama.

From Salon • Apr. 28, 2025

For that, they compared the genomes of symbionts across the Isthmus of Panama with other lucinid symbiont genomes from around the world.

From Science Daily • Jun. 4, 2024

You’ll start out at sea level and head to the Isthmus, the narrowest part of the island at half a mile wide.

From Los Angeles Times • Jan. 8, 2024

Communication between southern Mexico and the Andes required either a sea voyage or else a long chain of overland contacts via the narrow, forested, never urbanized Isthmus of Darien.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

Related Words

• collar