How to determine the morphologic tag of the word jovens?

Apparently, we might be tempted to consider it immediately a noun for the following reasons:

1. it can be modified by adjectives and numerals (duas ; primeiras)
2. it admits determiners (in this case the definite article, "a")
3.it is surely the Head of the noun phrase (np) holding the syntactic function of Subject (@SUBJ).

However, the same word can also belong to the morphological word class of the adjectives.
Focusing on the following example:
 

(1) As duas primeiras moças jovens fraquejam.

jovens is undoubtedly an adjective (fulfiling the adjective-noun agreement in gender and number).

The reason why there can be a word belonging to different morphological classes has to do, in this case (adjective and noun) to the fact that some sufixes like [nte] produce adjectives and nouns (ex: resistente, batente).
On the other hand, should we consider lexemes as doente, velho, vivo, morto, pobre, rico, and so on, to belong to both morphological classes, adjective and noun?
It seems acceptable that when the lexeme exists in the adjective form, so it does in the noun form:

(2) jovem [adj]     ---------- jovem [n]

 but the reverse is not true:

      *mulher[adj]    ---------- mulher [n]
 

However, there are many cases where this one to one relation does not occur. For instance, take the case of quente:

(3) A adesão da Câmara Municipal à comunidade portuária de Aveiro foi um dos pontos mais quentes da noite (...) -
 

No question as to consider quente an adjective. However, it does not fit into a nominal reading (like, for instance, its antonym frio would):

(4) *O quente  é pouco tolerado por muita gente. (should be o calor)

but

(5) O frio é geralmente pouco tolerado.
 

And even frio, with both nominal and adjectival readings, would not completely fulfil the semantics either.
Frio in (5) is an abstraction, a concept, which appears to be a different case from jovem which,  as a nominal reading, would not mean the concept of juventude, but rather a person. Therefore, one is tempted to consider that there is, in the latter case, an implied noun-head.

So, when the nominalised adjective implies a noun-head, the tag <n> was added. On the other hand,  the adjectives that in the nominal form are abstract concepts (not implying, therefore, a noun-head), are lexicalised as nouns.
 

Syntactically, the introduction of the tag <n> will help to determine the Head of the noun phrase, especially in the case where two adjectives occur, as in the following example:

(3) O velho simpático é feliz.

In this case velho would have the secondary tag <n>, which would be sufficient to consider it the HEAD of the np and simpático the post modifier (N<).

Another example can be found in sentence C142-1.