A perch can be more or less anything a person or animal sits on, as long as its feet are off the ground.
Bar stools are bafflingly popular at the moment, so you may even have a perch somewhere in your own home.
A perch is also a measurement, either of distance (sixteen and a half feet (or 5.03 metres in your money)) or, if you're measuring stone, of volume. This sort of a perch is sixteen and a half feet by one and a half feet by one foot, which is the same as 0.700842 cubic metres or, if you want to keep things simple by carrying on working in imperial measurements, 0.916667 cubic yards.
A perch is also a pole joining the two axles of a carriage together, a frame for inspecting cloth, or, of course, quite a lot of different sorts of freshwater fish.
This very beautiful fish is a white perch, Morone americana.
The fish word is completely separate from the others. It is also very seldom to be seen inhabiting bar stools.
Spot the Frippet: perch. The fish word comes from the Old French perche, and is probably something to do with the Greek perkos, which means spotted. The other sorts of perches come from the Latin pertica, which means long staff.