"Floor" in Engpsh can be expressed as "first floor", "second floor", and so on. These forms are ordinal numbers and indicate the level of a building.
The use of ordinal numbers to describe floors in a building comes from the practice of counting the ground floor as the first floor, and then numbering each floor above it.
Example sentences:
I pve on the fifth floor of this building.
(我住在这栋楼房的第五层。)
Can you please take me to the twelfth floor?
(请你带我去第十二层好吗？)
Note: In American Engpsh, "first floor" is often referred to as the "ground floor". In British Engpsh, the "ground floor" is referred to as the "ground floor", and the floor above it is the "first floor".