Mile

The mile (symbol: mi) is a unit of length. There are many different kinds of mile but mile on its own usually means the statute mile.

Statute mile 
In the US and the UK the word mile usually means the statute mile. 

 Feet  Yard  Chain  Furlong  Mile Kilometres 5,280  1,760  80  8  1  1.609344

Nautical mile
The nautical mile is used for sea or air travel. 

The nautical mile was originally defined as one minute of arc along a line of longitude of the Earth.  There are 60 minutes of arc in one degree or arc (60' = 1°). So there were 10,800 nautical miles from the North Pole to the South Pole.

Now the nautical mile is defined as 1,852 metres.

{|
|-
|1 nautical mile||= 1,852 metres (by definition)
|-
|||≈  feet
|-
|||≈  statute miles
|}
The speed of a ship that travels one nautical mile in one hour is called one knot.

The similar geographical mile is 1855.3 km. It was also one minute of arc, but along a line of latitude rather than longitude.

Roman mile
The mile was first used by the Romans.  It comes from the Latin phrase mille passus (plural: milia passuum).  This means "one thousand paces". A pace is the distance each foot moves when taking one step. 

“the Roman pace, measured from the heel of one foot to the heel of the same foot in the next stride”

{|
|-
|1 Roman mile||= 1,000 Roman paces (by definition)
|-
|||≈ 1,479 metres
|-
|||≈ 4,852 feet
|}

Other miles
Different miles have been used throughout history in various parts of the world. In Norway and Sweden, for example, a mil is a unit of length which is equal to 10 kilometres.

Idioms
Even in English-speaking countries that use the metric system (for example, Australia, Canada, and New Zealand), the mile is still used in many idioms. These include:
 A country mile is used colloquially to mean a very long distance.
 "A miss is as good as a mile" (failure by a narrow margin is no better than any other failure)
 "Give him an inch and he'll take a mile" – a corruption of "Give him an inch and he'll take an ell"Concise Oxford English Dictionary (5th edition; 1964). Oxford University Press. (the person in question will become greedy if shown generosity)
 "Missed by a mile" (missed by a wide margin)
 "Go a mile a minute" (move very fast)
 "Talk a mile a minute" (speak very fast)
 "To go the extra mile" (to put in extra effort)
 "Miles away" (lost in thought, or daydreaming)
 "Milestone" (an event showing a lot of progress)

References

Category:Imperial units
Category:Units of length