\begin{definition}[Definition:Imperial/Area/Acre]
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.
{{begin-eqn}}
{{eqn | o = 
      | r = 1
      | c = '''acre'''
}}
{{eqn | r = 4
      | c = roods
}}
{{eqn | r = 10
      | c = square chains
}}
{{eqn | r = 160 = 4 \times 40
      | c = square rods, poles or perches
}}
{{eqn | r = 4840 = 22 \times 220
      | c = square yards
}}
{{end-eqn}}
:810px
\end{definition}