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A fathom is the name of a unit of length in the Imperial system (and the derived U.S. customary units). The name derives from the Old English word fæðm meaning 'outstretched arms'.^[1][2][3] In Middle English it was fathme. Its size can vary from system to system. The most commonly used fathom today is the international fathom. There are 2 yards (6 feet) in a fathom.^[4]

Contents 1 International fathom 2 British Fathom 3 Use of the fathom 4 Trivia 5 Algorithmic Fathom 6 Other fathoms and similar units of length 7 See also 8 Notes 9 References 10 External links

In 1958 the United States and countries of the Commonwealth of Nations defined the length of the international yard to be 0.9144 metres. Consequently, the international fathom is defined to be equal to 1.8288 metres.

1 international fathom is equal to:

• 6 feet (1 foot is about 0.1667 fathoms)
• 2 yards (1 yard is exactly 0.5 fathoms)
• 1.8288 metres (1 metre is about 0.5468 fathoms)
• 72 inches

Prior to that standarization on the international fathom, the British Admiralty defined a fathom to be a thousandth of a imperial nautical mile (which was 6080 ft) or 6.08 feet. This is equivilent to 1.853184 metres.

Once also used for measuring distances on land, the fathom is now restricted to nautical uses, especially expressing the depth of water or the length of nautical rope or cable. Until early in the twentieth century, it was the unit used to measure the depth of mines in Cornwall, England.^[5] The verb "to fathom" means to measure the depth of something, especially using a sounding line.

Civilian maps in English-speaking countries used to have depths commonly marked in fathoms, but this has changed to metres generally, even in US maps. Nautical charts have changed on a separate schedule.

It is customary, when burying the dead in the USA and elsewhere, to inter the corpse at a fathom's depth, or six feet under.

In algorithmic techniques such as the Branch-and-Bround technique, fathoming refers to eliminating a subset of possible solutions because these solutions can never be the optimal solution.

Units of length similar to the size of the fathom can be found in many cultures. Some are listed below.

Culture	Name	Length in metres
Croatian	hvat	1.896484
Czech	sáh	n/a
Danish	favn	1.883124
Dutch	vadem, vaam	1.883679
Esperanto	klafto	n/a
Estonian	süld	n/a
Finnish	syli	n/a
French	toise (circa 1150), brasse (1409)	~1.949
German	klafter	n/a
Ancient Greek	orguia	1.8542
Hungarian	öl	1.8964838 (Viennese)
Interlingua	fathom	n/a
India (State of Manipur)	Sana lamjel	n/a
Italian	braccio	n/a
Japanese	hiro(尋)	~1.818
Maltese	qasba	~2.096
Norwegian	favn	2
Polish	sążeń	1.728
Portuguese	braça	n/a
Russian	morskaya sazhen (морская сажень)	1.852
Sanskrit	vyama	n/a
Serbian	hvat (хват)	n/a
Slovak	siaha	n/a
Spanish	braza	n/a
Swedish	famn	1.7814

• English unit
• Imperial unit
• United States customary units
• International System of Units
• Ancient Greek units of measurement

1. ^ Oxford English Dictionary, second edition, 1989;
2. ^ Bosworth / Toller: An Anglis-Saxon Dictionary, 1921.
3. ^ http://beowulf.engl.uky.edu/cgi-bin/Bosworth-Toller/ebind2html3.cgi/bosworth?seq=285
4. ^ Encyclopædia Britannica eleventh edition 1911.
5. ^ Buckley, J.A. (1992). The Cornish Mining Industry. Penryn, Cornwall: Tor Mark Press. ISBN 0-85025-334-9. 

• Fenna, Donald (2002). A Dictionary of Weights, Measures, and Units. Oxford University Press. ISBN 0198605226. 

• An explanation of the fathom marks used at sea (retrieved Sept 2005).
• Hungarian web page that refers to the length of a "bécsi öl"