I'm a bit confused about the description of grammar in Latin.
For example Orberg has in Exercitia Latina the following: Plusquamperfectum passivi constat ex participio perfecti et praeterito imperfecto verbi 'esse'.
I get confused as to when / whether / if words like 'passivi' and 'imperfecto' have to be used the way he uses them. To explain my question. I had written 'Plusquamperfectum passivum' - thus 'passivum' as an adjective. So he has 'passivi' to show the meaning 'Pluperfect OF the passive', right? But then he has '...et praeterito imperfecto....'. Could I have written '...et praeterito imperfecti...'?
Is there a good overview of the grammar of discussing grammar (I see a chapter later in LLPSI dealing with grammar so perhaps I should wait for this..)?? I'd be grateful for any thoughts... Because I'd like to be able to use more or even all latin when discussing grammar on this forum but I'm not clear about whether things have to be written as they are...