The Sound (Danish Øresund, Danish pronunciation: [ˈøːɐsɔnˀ], or Swedish Öresund, pronounced [œrəˈsɵnd]), locally known as Sundet, is the strait that separates the Danish island Zealand from the southern Swedish province of Scania. Its width is just 4 kilometres (2.5 mi) at the narrowest point between Kronborg Castle at Helsingør in Denmark, and the northern harbour of Helsingborg in Scania, Sweden. The strait has also lent its name to the Øresund Region of 3.8 million inhabitants on both the Danish and Swedish sides.
The Øresund Bridge (which includes a 3 km tunnel) between Danish capital Copenhagen and the largest city of Scania, Malmö was inaugurated on 1 July 2000 by Queen Margrethe II of Denmark and King Carl XVI Gustaf of Sweden. Ferries run around the clock between Helsingborg, Sweden and Helsingør, Denmark.
The oldest known name of the strait is urasu[n]ti which appears on a runestone from about 950 and it was locally known as Oresund in the 13th century. The strait is today called Øresund in Danish and Öresund in Swedish, informally Sundet in both languages. The prefix ør(e) means gravel beach and a sund is a sound or narrow seaway.
Streams, animals and salinity 
Øresund, being at the border between oceanic salt water (with a salinity of more than 30 PSU) and the Baltic sea (only 3–7 PSU) has rather unique water conditions. The streams are very complex, but the surface stream is often northbound (from the Baltic sea) which gives a lower surface salinity, though streams can change from one day to another. The average surface salinity is about 10-12 PSU in the southern part but above 20 PSU north of Helsingør. At the bottom of the sea, conditions are more stable and salinity is always oceanic (> 30 PSU) below a certain depth that varies between 10 and 15 metres. In the southern part, however, the depth is just 7–10 metres, and this is the definite border of oceanic salt water, therefore also a border for many maritime species of animals. In the central Baltic Sea only 52 known salt-water species resided compare with around 1500 in the North Sea. Close to 600 species are known to exist in at least some part of Øresund. Well-known examples, for which the bottom salinity makes a distinct breeding border, include lobster, small crabs (Carcinus maenas), several species of flatfish and the burning jellyfish (Cyanea Article); the latter can sometimes drift into the southwest Baltic sea, but it cannot reproduce there.
Political control of Øresund has been an important issue in Danish and Swedish history. Denmark maintained military control with the coastal fortress of Kronborg at Elsinore on the west side and Kärnan at Helsingborg on the east, until the eastern shore was ceded to Sweden in 1658. Both fortresses are located where the strait is just 4 kilometres wide.
In 1429 King Eric of Pomerania introduced the Sound Dues which remained in effect for more than four centuries, until 1857. Transitory dues on the use of waterways, roads, bridges and crossings were then an accepted way of taxing which could constitute a great part of a state's income. The Sound Dues remained the most important source of income for the Danish Crown for several centuries, thus making Danish kings relatively independent of Denmark's Privy Council and aristocracy. The Copenhagen Convention of 1857 abolished the Dues and made the Danish straits an international waterway.
Notable islands 
- Ven (also spelled Hven)
- Peberholm - an artificial island
- Middelgrundsfortet - an artificial island
- Flakfortet - an artificial island
- Gråen - a semi artificial island outside port of Landskrona
See also 
|Wikimedia Commons has media related to: Oresund|
- "Bælthavet og Sundet" (in Danish). Danish Meteorological Institute. Retrieved 30 March 2013.
- Gluver, Henrik; Dan Olsen (1998). "2.7 Øresund Bridge, Denmark-Sweden". Ship Collision Analysis. Rotterdam: A. A. Balkema. ISBN 90-5410-962-9. "Øresund (the Sound) is, like the Great Belt, an important water way for the international ship traffic between the North Sea and the Baltic Sea."
- "Udvalgte stednavnes betydning" (in (Danish)). Københavns Universitet. Retrieved 2011-04-27.
- Menefee, Samuel Pyeatt, "The Sound Dues and Access to the Baltic Sea" in Renate Platzoder and Philomene Verlaan (eds.), The Baltic Sea: New Developments in National Policies and International Co-Operation (1996), pp. 101–32.
- Øresunddirekt - Official public information site for the inhabitants of the Øresund region
- Øresund Trends - An official public information site with up-to-date information on the region, available in English
- Øresundstid - The History of the Øresund Region (English, Swedish, Danish)