In my post Morphological Parts of Speech in Greek last year, I presented a model of five or six parts of speech based purely on what they inflect for. I just found out Varro suggested similar for Latin over two thousand years ago.
In his article Dionysius Thrax vs Marcus Varro in Historiographia Linguistica 17:1-2 (1990), Daniel Taylor argues for the greater significance of Varro over Thrax in the history of Greco-Roman lingustics.
I actually started reading the article for comparisons made with Theodosius but his description of Varro’s parts of speech caught my eye. After introducing Thrax’s list of eight parts of speech for Greek (noun, verb, participle, article, pronoun, preposition, adverb, and conjunction) which has dominated since, he describes Varro’s for Latin:
His definitions are exclusively grammatical, and there are but four parts of speech: one with case, one with tense, one with both, one with neither.
This results in a similar division to the first table in my earlier blog post although conflates infinitives and finite verbs (which Thrax does as well).
It’s certainly appealing as an initial taxonomy of parts of speech, for Greek as well as Latin.