Enumeration is the name given to the generic field of mathematics which deals with counting objects. The counting is abstracted as far as possible from the objects in question - to come up with counting techniques that are generic and do not rely on the properties of any specific group of objects.
... impressive Iguaçu[?] falls, the Rio Negro, São Francisco[?], Xingu, Madeira and the Tapajós[?] rivers.
Situated along the equator, Brazil's climate is predominantly ...