The rod is a historical unit of length equal to 5+1⁄2 yards. It may have originated from the typical length of a mediaeval ox-goad. There are 4 rods in one chain.
The furlong (meaning furrow length) was the distance a team of oxen could plough without resting. This was standardised to be exactly 40 rods or 10 chains.
An acre was the amount of land tillable by one man behind one team of eight oxen in one day. Traditional acres were long and narrow due to the difficulty in turning the plough and the value of river front access.
An oxgang was the amount of land tillable by one ox in a ploughing season. This could vary from village to village, but was typically around 15 acres.
A virgate was the amount of land tillable by two oxen in a ploughing season.
A carucate was the amount of land tillable by a team of eight oxen in a ploughing season. This was equal to 8 oxgangs or 4 virgates.
