Floors of a Commercial Building
See also: Floors Of A House
There are some important differences between British English (BrE) and American English (AmE) in talking about the floors in a commercial building.
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 building). 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:
Many commercial buildings also have a "mezzanine" floor, which is a kind of "half-floor". This diagram shows a six-storey building that has a mezzanine and two basement levels below.
A floor is the same as a storey: all the rooms that are at the same level