To be more precise, vAkyArtha and padArtha are the subject matter of the book.
In fact, the topic of each samuddEs'ya is a padArtha. These padArtha-s are not word meanings; they are in fact categories of word-meanings.
Though this word padArtha is used in nyAya and vais'Eshika too, there padArtha-s are entities and are not necessarily categories of word-meanings. But in vAkyapadIyam, they are essentially categories of word-meanings only.
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विशेषण means specifying, the word that specifies, qualifies. Hence it always requires a विशेष्य, the qualified.
In सुंदरीं बालां पश्यामि, the विशेष्य - विशेषण relationship is explicit. बाला is विशेष्य and सुन्दरी is विशेषण here.
When सुन्दरी बाला = beautiful girl, then विशेष्य - विशेषण relationship is explicit again. बाला is विशेष्य and सुन्दरी is विशेषण here too.
When सुन्दरी बाला = सुन्दरी च बाला च as in सीता सुंदरी बाला (अस्ति) then ' "सुन्दरी बाला" इत्यत्र द्वावपि शब्दौ विशेषणे स्तः |' is correct. Even in सीता सुंदरबाला (अस्ति), "सुन्दरी बाला" इत्यत्र द्वावपि शब्दौ विशेषणे स्तः is correct.
In तत्सुंदरी बाला (अस्ति), बाला is विशेषण and सुन्दरी is विशेष्य .
In तद्बाला सुंदरी (अस्ति) बाला is विशेष्य and सुन्दरी is विशेषण .
सा बाला अस्ति । can mean She is a girl or That person is a female and is in childhood.
When it is used as equivalent to 'she is a girl' , बाला sounds to be a noun. When it is used in the sense of That person is a female and is in childhood, बाला sounds to be an adjective. Thus a subanta has an inherent potential to be a nominal or adjectival word.
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