One of the major constituents of the initial massive overhead required in learning ancient Greek is the participle. Participles are extremely important in ancient Greek; where possible, it seems, it’s preferable to a finite verb. Because they decline and agree in gender, number, and case with what they modify, participles seem complicated compared to English; on the other hand, this reduces the ambiguity that can exist in English with participles, a la “I saw the dog running down the street.” Is it “I” or “the dog” which is running down the street in that sentence? In ancient Greek, however, there would be no confusion — the participle would either be in the nominative case, meaning it would agree with the subject “I”, or it would be in the accusative case, meaning it would agree with the direct object of the main verb “saw”, “the dog”. In English, having lost most of our inflection, we depend on word order and proximity, as well as context, to tell us grammatical function, so the only real way to distinguish whether it’s I or the dog running down the street is to change the sentence to “Running down the street, I saw the dog,” which unfortunately seems a little stilted and artificial. “I saw the dog while running down the street” is a little better, but it seems to imply the imperfect periphrastic “while I was running down the street,” which starts to edge away from a pure use of a participle.
Modern Greek’s participles, it turns out, do not decline. This means there isn’t as much to learn at the outset, but it also means that the ambiguity you have in English exists in Modern Greek:
Είδα τον Πέτρο πηγαίνοντας στο σπίτι μου -> I saw Peter going to my house. (Not clear if it’s the subject, “I”, or the object, “Peter”, going to my house.)
As opposed to ancient Greek, where you can do this:
Εἴδον/Ἔβλεπα τὸν Πέτρον βαίνοντα εἰς τὸν οἴκον μου. Here, the participle βαίνοντα is in the accusative case, making it clear that it’s Peter going to my house. Also, because of the inflection, you can manipulate the word order in all kinds of ways and have it make sense regardless:
Εἴδον/Ἔβλεπα τὸν Πέτρον τὸν βαίνοντα εἰς τὸν οἴκον μου. Literally, “I saw Peter, the one going into my house.”
Εἴδον/Ἔβλεπα τὸν βαίνοντα εἰς τὸν οἴκον μου Πέτρον. Literally, “I saw the going-into-my-house Peter.”
But then you can also do this:
Εἴδον/Ἔβλεπα τὸν Πέτρον βαίνων εἰς τὸν οἴκον μου. Here, the participle βαίνων is in the nominative case, making it clear that it agrees with the unexpressed subject “I” (unexpressed since the -ον/-α ending of the verb already makes it clear that we’re in the first person).
All of this is to say — here’s to inflected languages. Pay now or pay later.