Perimeter != Circumference

[estianross]

https://docs.quantifiedcode.com/python-anti-patterns/maintainability/using_the_global_statement.html#encapsulate-the-global-variables-into-objects

For a rectangle, the proper term is "perimeter," not "circumference"; Circumference is reserved for circles, ovals, and other non-regular 2-D shapes with no corners. Perimeter is a sum of sides, circumference is the value of the magnitude of outer limit of a shape with no sides.
This inconsistency of the wording across this page may cause confusion to non-native speakers of English when reading the example solution provided.