ekfu fu'ivla

x1 is the return value of a function without body (with possibly more arguments)

x1 can be void. Two main interrelated usage cases: 1. wrapped into a sumti and used as a dummy predicate to fill in arguments of higher-order functions with stricter typing of its argument, for which ekfu is used. Similar to the concept of object in object-oriented programming. 2. as type-signature template.