An acre is a measure of land area in both the US Customary and the Imperial systems of measurement. It is the area of a rectangle one chain (22 yards or 66 feet) by one furlong (220 yards or 660 feet), an area of 4840 square yards or 43,560 square feet.
Derivation and traditional usage
The Oxford English Dictionary defines the word acre in its original sense as a piece of arable land deriving from the Old English æcer and various northern European varieties of it – ekker, acker, ackar etc., The word ajra in Sanskrit means field as does agros in Greek and ager in Latin.
It came into Middle English as a piece or plot of arable land, before being delineated as an area that could be ploughed (plowed) by a yoke (pair) of oxen in a day. Later statutes decided it should be 220 yards long by 22 yards broad although, centuries later, Shakespeare would not have been referring to particular measurements when he wrote between the acres of the rye these happy country folk would lie. ("As You Like It") The same would have applied to the Wiltshire folksong that surfaced in the mid nineteenth century: My father left me an acre of land.
The surname Ackerman (and its variations) means man who owns or works a plot of land.
It is surely no coincidence that a cricket pitch is 22 yards (now 20 metres) long. The measure of length, furlong, now used only in some English speaking countries as a distance in thoroughbred horse racing, is the length of a furrow in the traditional acre (OE fura + lang.)
In those countries that now use the metric system of weights and measures, the term is still used colloquially, usually in the plural, to signify expanse, often in the real estate industry. Acreage is a commonly used term.