Floors of a House
See also: Floors Of A Commercial Building
There are some important differences between British English (BrE) and American English (AmE) in talking about the floors in a house.
In BrE the floor at the level of the surrounding land or ground is called the ground floor (this is the floor where you usually enter a house). In AmE the same floor is called the first floor. The floors above are numbered starting from the ground or first floor, so there is usually a difference of one level in BrE and AmE usage, as follows:
This diagram shows a two-storey house that also has a basement level underneath.
A floor is the same as a storey: all the rooms that are at the same level