on the
It is amazing how many different names there are for domestic making hot water (and storage).
US Water Heater (ours tend to be Glass lined steel with about 7-12Y life. Tho as Jon mentioned, there are demand type, and those that used the house heating boiler with a heat exchange insert)
Britain (only?) Cylinder
My Russian neighbor called it a "boiler" (Note: you really do not want it any way near Boiling. About 250 degrees F at 40 PSI
)
Others?