Some Grammar for prepositions, as taught to Greek students of High School ("Γραμματική Νέας Ελληνικής Γλώσσας (Α-Β-Γ Γυμνασίου)" here: http://ebooks.edu.gr/modules/ebook/show.php/DSGYM-A112/621/4006,17977/ )
"The prepositions that are used in Modern Greek are:
a) The Common, which are very often used, e.g. Αυτός ήλθε από την πόλη.
b) The Literary (or Archaic), derived from the ancient Greek and used in a very typical style and stereotypical expressions, e.g. O Περικλής έζησε τον πέμπτο αιώνα προ Χριστού (Pericles lived in the 5th century B.C.). Note: Here προ Χριστού can abbreviate as π.Χ. but A.C. is μετά Χριστόν, or μ.Χ. abbreviated).
Some prepositions sometimes operate as adverbs, sometimes as conjunctions and sometimes as prepositions, e.g. Η πυροσβεστική έφτασε μετά την αστυνομία= The fire brigade arrived after the police (as preposition here) and Ο Γιώργος έφτασε μετά=George arrived afterwards (as adverb).
The two kinds of prepositions presented here:
αντί=instead, από=from, by, για=for, δίχως=without, εναντίον=against, εξαιτίας=because of, έως=until, ίσαμε= about, more or less, equal with, κατά=during etc , με=with, μετά=after, μεταξύ=between, among, μέχρι=till, until, παρά=despite, πριν=before, προς=to, σαν=like, σε=in, χωρίς=without, ως=as.
Literary or Archaic
ανά=per, άνευ=without, διά=for, εις=in, εκ=out, εκτός=except, εν=in ένεκα=because of, εντός=in, inside, επί=on, κατόπιν=after, λόγω=because, μείον=less, minus, μέσω=through, by, περί=about, laying, concerning, πλην=except, minus, προ=before, συν=plus, υπέρ=, υπό=under, below, χάριν=sake.
Besides the two types of prepositions there are compound prepositions (or multi-word) prepositions which are prepositions or combinations thereof (e.g., εκτός από=except for, πριν από=before, etc.) or adverb combinations with prepositions (e.g.έξω από=outside, μέσα σε=inside etc).
The prepositions are used either alone or as first part of compound words. The prepositions, which are used only in syntax are:
για, δίχως, εναντίον, εξαιτίας, έως, ίσαμε, με, μεταξύ, μέχρι, πριν, σαν, σε, χωρίς, ως.
άνευ, εκτός, ένεκα, εντός, κατόπιν, λόγω, μείον, μέσω, πλην, χάριν.
All others used in syntax and composition of words.
Nouns, adjectives, pronouns and numeric that follow the prepositions are normally in accusative, e.g. Αυτός ήλθε με το γιό του= He came with his son. But it is possible, after certain prepositions,to be in genitive, eg Αυτή η επιτυχία φαίνεται σαν δώρο εξ ουρανού (Archaic)=This success seemed like a gift from heaven, or even nominative, e.g. Αυτός έγινε από δήμαρχος, κλητήρας ( δήμαρχος=mayor, κλητήρας=clerk, bailiff, a usual Greek proverb).
In speech some changes happen in the form of prepositions, which are derived from elision (έκθλιψη) of the final and removal (aphaeresis, αφαίρεση) of the initial vowels, e.g. με ένα βιβλίο → μ'ένα βιβλίο, από τα άλλα → απ'τ'άλλα.
In the case of meeting the preposition από with an article genitive or causative the final ο in από is eliminated, e.g. από τά άλλα → απ'τ'άλλα. The changes depend on the rate of speech in oral speech or the speech type or on the author's preferences in writing.
Finally, the preposition σε, when found before the accusative and the generitive of the article, it forms with it one, single word, eg σε+του=στου, σε+τον=στου etc.
The translation is mine, I used the Google translation, so please correct my faults you find. I added some notes only and the translation of the examples to the above Greek text to be more understandable by non-Greek speakers.
With pronouns you can say either πίσω or πίσω από, just remember to use the genitive after the former and the accusative after the latter: είναι πίσω της, είναι πίσω από αυτή. With everything else use πίσω από: πίσω από το τραπέζι (behind the table), πίσω από την καρέκλα (behind the chair), πίσω από έναν τοίχο (behind a wall).
How do I know which prepositions take a genitive, and which take an accusative? Is there a list?
As a rule, after a preposition the accusative is used.
In the example above, πίσω is an adverb, not a preposition. As I mention in my other comment in this discussion it's the case of the pronoun straight after the adverb, that needs to be the genitive. After a preposition it would still be the accusative.
Πίσω in this case is definately a preposition. Maybe normally it is an adverb(?) but here it acts like a preposition! So the case only depends on the presence of the preposition απó as I understand..
Πίσω is an adverb in Greek and this categorisation is not flexible depending on any given phrase. Parts of speech like prepositions do not necessarily have a single way in which they dictate structure.
As a rule, after a preposition the accusative is used.
However, some prepositions, like επί, take the genitive case. Sometimes, even the nominative is used after από: http://ebooks.edu.gr/modules/ebook/show.php/DSGYM-A112/621/4006,17977/ That's what my comment refers to.
How can I follow a discussion when I'm not on the pc? There is no "Follow discussion" button.
Thank you for this discussion. πίσω is a new word for me. I was wondering how modern Gk would say "behind." Prepositions are always tricky. I was wondering how modern Gk navigates "behind" and "after." Ancient Gk used μετά, "after," temporally + accusative, which seems to be how it is still used in modern Gk (based on reading through this discussion here). It's interesting to learn that πίσω is + genitive while πίσω από is + accusative. Mandeson's old dictionary says πίσω is an adv. and means "back," so I guess πίσω από = "back from," i.e., behind.