Will a single room be suitable for two young adults on their honeymoon?
No, a single room means a single bed, what we would consider a twin. I usually get single rooms in Europe when I'm traveling myself and sometimes they're barely big enough for me to maneuver around, I can't imagine sharing that little space! You definitely will want a double!
The bigger issue is that, in Germany, at least, Gastgeberen rent a single room to a single person. It's not about the number of people in the bed, it's the bath linen they will use, the hot water they will use, and the breakfast they will consume. I have seen accommodations where the charge was per person, whether they were in one room or two. You might ask their permission. Tell them you want a single room with a rollaway bed, but I'm sure they will charge extra for a second person in a single room.
It is not just Germany, it is everywhere. A "single" room means one person, not one bed. Two people must book a "double", which can be one bed, but you need to pay for two people for the reasons Lee mentioned.
thanks, wanted to clear that up.
AJ - In addtion, for many places in Europe a double mostly means two single beds, not always a double bed.
SO find out the correct term to ask for when booking your room.
In Italy, it would be letto matrimoniale, a double bed suitable for two people.
Ron brings up a very good point about double meaning two single beds in most of Europe. If you are asking for a room with one double bed, you will usually get two twin-sized beds pushed together, each made up with its own set of sheets, so it can make cuddling with your spouse difficult.