what is isthmus

An isthmus is a narrow strip of land connecting two larger land areas, usually with water on either side.

Canals are often built across isthmuses, where they may be a particularly advantageous short cut for marine transport. The Panama Canal crosses the Isthmus of Panama, connecting the North Atlantic and Pacific Oceans;  the Suez Canal connects the Mediterranean Sea and the Indian Ocean, cutting across the western side of an isthmus formed by the Sinai Peninsula.