Meaning of FLOOR in English
(LEVEL OF BUILDING) [noun] [C] - a level of a building; a storeyTake the elevator to the 51st floor.We live on the third floor.The ground floor apartment (= the apartment at road level) is for sale.The second floor (= the people who live/work on the second floor) aren't very friendly.USAGE: In British English the first floor of a building is the level above ground level. In American English the first floor of a building is at ground level.
Cambridge English vocab. Кембриджский английский словарь. 2012