But is also clear that it was normal to address your parent as
'pater'.
Is this clear?
To establish this I think we'd need examples of quoted direct speech
by Greek speakers of the period who were referring to their fathers.
Outside direct speech, the terminology would be dictated by genre and
other considerations, factors which would complicate the analysis.
So this raises the question: are there examples of quoted direct
speech indicating that ho pater (note the article!) was normative?
How do these compare to texts where, for example, pappas appears?