The values common (c) and invariant (n), presented in the Italian and Spanish tables, for the attributes Number and Gender respectively, raise an important issue: they are not a gender or a number, but they are a signal that gender or number cannot be determined from the form of the word alone. Ontologically, they have a quite different status from m and f. They can be seen as a metalinguistic device or as a third value: this can be seen as a kind of multilabel whose semantics is a disjunction operation. In fact, the value e.g. n is a macro for sg pl. It is used for the lexicon encoding of the series of the Italian invariant nouns. For these nouns, the number can be decided in the context only on the basis of syntactic considerations, i.e. by observing the agreement with other elements, articles, verbs, adjectives, as in:
``Parigi é una cittá europea; le cittá europee''.
Sometimes the number can remain undecided, notwithstanding the context, i.e. when the noun agrees with invariant adjectives. The same is true for the common gender:
``un bravo insegnante, una ottima insegnante''.