The acre is a unit of area and is used in the imperial and US customary systems with the symbol a.
It represents the area the size of one chain by one furlong (66 by 660 feet). This is exactly equal to 10 square chains, 1⁄640 of a square mile or 43,560 square feet.
It is generally used to measure the size of land.
The square yard is a unit of area and is an imperial unit with the symbol ya².
One square yard is equal in area to a square with edges one yard in length. It also equals 1,296 in² and ≈ 0.836 m².
The square yard is a common unit of measurement in the UK and US.