Definition:Imperial/Area/Acre

Definition

The acre is an imperial unit of area.

One acre is equal to an oblong measuring $1$ chain by $1$ furlong.

That is, measuring $4$ rods, poles or perches by $10$ chains.

 $\ds$  $\ds 1$ acre $\ds$ $=$ $\ds 4$ roods $\ds$ $=$ $\ds 10$ square chains $\ds$ $=$ $\ds 160 = 4 \times 40$ square rods, poles or perches $\ds$ $=$ $\ds 4840 = 22 \times 220$ square yards

Historical Note

The acre is a traditional measure of land arising from the days of ploughing in mediaeval times and earlier.

It was defined as the area of land that could be ploughed by $1$ ploughman with $1$ ox in $1$ day.

It is noted that an acre is not actually defined as a square area, but as an oblong strip $10$ times as long as it is wide.

The reason is readily apparent: its length is, as is apparent from its definition, one furlong, that is, furrow-long.

Linguistic Note

The word acre derives from the Old English æcer, meaning open field.

It is pronounced ay-ker, and was at one time spelt aker.