Fathom
unit of length in the old imperial and the U.S. customary systems
A fathom is a unit of length in the imperial and U.S. customary systems equal to 6 feet (1.8288 m), used especially for measuring the depth of water. The fathom is neither an international standard (SI) unit, nor an internationally accepted non-SI unit. Historically, it was the maritime measure of depth in the English-speaking world but, apart from within the US, charts now use metres.
There are two yards (6 feet) in an imperial fathom. Originally the span of a man's outstretched arms, the size of a fathom has varied slightly depending on whether it was defined as a thousandth of an (Admiralty) nautical mile or as a multiple of the imperial yard. Formerly, the term was used for any of several units of length varying around 5–5+1⁄2 feet (1.5–1.7 m).
Etymology
The term (pronounced ) derives (via Middle English fathme) from the Old English fæðm, which is cognate with the Danish word favn and means "embracing arms" or "pair of outstretched arms". It is maybe also cognate with the Old High German word "fadum", which has the same meaning and also means "yarn (originally stretching between the outstretched fingertips)".
Forms
Ancient fathoms
The Ancient Greek measure known as the orguia (Ancient Greek: ὀργυιά, orgyiá, lit. "outstretched") is usually translated as "fathom".
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