"Our conversation is interesting."
Translation:Η συζήτησή μας έχει ενδιαφέρον.
Communication is the direct translation of επικοινωνία.
So,communication and conversation do have a difference.
Communication can be one way. It might be something you want to tell or convey to someone. (exp. You can communicate with someone with your eyes alone.)
Conversation on the other hand can take place only if there's a return statement. You convey something , the other person replies. That makes a conversation. ^.^
Then you would have to turn the noun ενδιαφέρον "interest" into an adjective -- so it will have to agree with the feminine noun συζήτηση and become ενδιαφέρουσα.
Η συζήτησή μας είναι ενδιαφέρουσα is another accepted alternative.
No, ενδιαφέρουσα is indeed the correct answer.
This adjective belongs in a special category of adjectives, ending in -ων (masc), -oυσα (fem), -ον (neut).
Other adjectives that are included in this category are μέλλων (future), πρωτεύων (primary), δευτερεύων (secondary), υπάρχων (existing) and επείγων (urgent).
If you have any further questions or concerns about this category's adjectives, feel free to ask.^.^
Hahahah, I'm not entirely sure. But it seems like there's an exception to almost every rule. :)