Isthmus (noun)

1. A narrow strip of land connecting two larger land areas, typically with water on either side.
2. A narrow strip of tissue connecting two larger parts of an organ, or connecting two organs.

Origin:

From the latin isthmus, from the greek ἰσθμός (isthmós), from ἴσθμι (ísthmī), to go, pass.

Examples:

1. The Isthmus of Panama connects North and South America.
2. The Isthmus of Suez connects Africa and Asia.
3. The Isthmus of Corinth is a narrow strip of land that connects the Peloponnese peninsula to mainland Greece.
4. The isthmus connecting the brain's cerebral hemispheres is called the corpus callosum.
5. The isthmus of the thyroid gland connects the two lobes of the gland.