There’s lots and lots of different systems: https://en.wikipedia.org/wiki/Yan_tan_tethera#Systems_by_region https://en.wikipedia.org/wiki/Yan_tan_tethera#System

There’s lots and lots of different systems: https://en.wikipedia.org/wiki/Yan_tan_tethera#Systems_by_region https://en.wikipedia.org/wiki/Yan_tan_tethera#Systems_by_reg.... Some have methera, some have pethera, many have something else.