The individual suites are seperated. They are apart- divided by walls.
The word originally meant a room seperated from the main building or house. These were rented out or used for special occassions or special people. Eventually someone came up with the idea to have a whole bunch of apartments in one building. I happen to live in an Apartment Complex. There are several buildings. Theses buildings are definitely apart from each other. Building 12 and building 11 are not “stuck together”.