...is it not "η ιδιοκτησία μου"?
σε "on, at, in, by" takes the accusative case, so η turns into την.
Then σε+την = στην.
Ah, well that explains exactly what I was misunderstanding, then. Thanks!
Είσαι (η) ιδιοκτησία μου. = You are my property.
I wrote είσαστε here and it was rejected. Couldn't this be you plural - 2 or more people wandered to the wrong place??
I wrote "εσείς είσαστε στην ιδιοκτησία μου" and was also rejected. I don't know why.
Είσαι πάνω στην ιδιοκτησία μου;