Hi Stella, an apartment is a place to live that you rent instead of own--generally not the entire building. A flat is an apartment on one floor--often the entire floor. A condo is a form of ownership of an individual apartment usually in a building of several apartments, most owned instead of rented. In NYC there is also Coop forms of ownership, which is ownership of shares of a building with the right to occupy a certain amount of space. It differs from the condo in that a condo provides traditional fee simple ownership, much as a townhouse, though townhouses are generally single family dwellings. - Sun Oct 26 2008, 13:49