perch

   1. an alternate name for the rod¹ (16.5 feet or 5.0292 meters), introduced in the twelfth century by the Norman conquerors of England. The word perch (perche in French: see below) comes from the Latin pertica (pole). The Romans also had a distance unit called the pertica, but it was shorter: 10 Roman feet (9.71 English feet or 2.96 meters).

   2. a unit of area equal to one square perch¹. A perch of area covers exactly 272.25 square feet or about 25.292 85 square meters. There are 40 perches in a rood and 160 perches in an acre.

   3. a traditional unit of volume for stone and other masonry. A perch of masonry is the volume of a stone wall one perch (16.5 feet) long, 18 inches high, and 12 inches thick. This is equivalent to exactly 24.75 cubic feet, 0.916 667 cubic yard, or about 0.700 842 cubic meter.

   4. a traditional unit of distance in Ireland standardized at 21 English feet (6.4008 meters) or 14/11 English perch or rod. Since the Irish perch was 27.27% longer than the English, the Irish chain, furlong, and mile were longer in the same proportion..

   5. a traditional unit of distance in French North America. The perche equals 18 pieds (see below) or 3 toises. By legal definition in Canada this equals 19.1835 English feet or 5.847 13 meters.

   6. a traditional unit of area in French North America, equal to one square perche¹. A perche of area is therefore equal to 0.01 arpent, about 368.007 square feet (40.8896 square yards) or 34.189 square meters.