YardA yard (abbr. yd) is an imperial unit of length, defined as 3 feet or 36 inches, which is exactly 0.9144 metres, presuming international inches are used.
The early yard was divided by the binary method into 2, 4, 8, and 16 parts called the half-yard, span, finger, and nail.
The yard derives its name from the word for a straight branch or rod, although the precise origin of the measure itself is not definitely known. Some believe it derived from the double cubit, or that it originated from cubic measure. One postulate was that the yard was derived from the girth of a person's waist, while another claim held that the measure was invented by Henry I of England as being the distance between the tip of his nose and the end of his thumb. These are believed to be more likely standardising events as opposed to an actual coining of the measure.
Several different standardisations of the yard have been produced over the years, resulting in yardsticks of various lengths. The modern yard is a compromise between the old British and American standards, and is calibrated against the metre.
A yard is also an enclosed area of land, usually tied to a building (eg. back yard, prison yard).
The Yard is the colloquial name for Scotland Yard: the headquarters of the Metropolitan Police Service who are responsible for policing Greater London (although not the City of London itself). See also: Liberty of the yard.