yard, abbr. yd, basic unit of length in the customary system of English units of measurement; all other units in the English system, such as the inch, foot, rod, and mile, are derived from it. Since 1893 the yard has been defined in terms of the meter, the basic unit of length in the metric system. For a long time the yard was held to equal 3600/3937 of a meter; it has since been recalculated so that 1 yd equals 0.9144 m. In the United States results of geodetic surveys are still expressed in feet based on the former definition of the yard; this is known as the U.S. Survey Foot, defined as 1200/3937 of a meter.
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