This feature (based on WALS feature 120, by Leon Stassen) is about the presence or absence of a copula in clauses with predicative noun phrases with class-inclusion function . Thus we study how a situation like ‘Mary is a singer’ is expressed in the APiCS languages. In class-inclusion constructions, the predicative noun phrase (‘a singer’) is indefinite and non-referential. We are disregarding predicative noun phrases with identification function as in ‘My sister is the woman next to the singer’, where the predicative noun phrase is definite and referential. Moreover, we restrict our comparison to stative situations, i.e. we leave aside situations like ‘Mary became a singer’.
A copula is defined as any overt element that occurs in such clauses apart from the subject and the predicative noun phrase and that does not normally occur in verbal clauses.