isthmus ĭs´məs [key], narrow neck of land connecting two larger land areas. Since it commands the only land route between two large areas and is on two seas, an isthmus has great strategical and commercial importance and is a favorable situation for a city. In modern times many isthmuses have been cut through by canals to eliminate the necessity of land transport. The most important isthmuses are the Isthmus of Panama, connecting Central and South America, and the Isthmus of Suez, joining Asia and Africa. Canals were dug through both of these. The Isthmus of Corinth between the Morea peninsula and central Greece also has a canal.

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