The term "third floor" refers to a level or story in a building that is three levels above ground level. In some buildings, it may also be referred to as the "upper third," indicating its position relative to other floors within the same structure.
The entire third floor of our house is going to become our retreat from the world! (theinspiredroom.net)
Find the art on the second and third floor galleries. (hamptonsarthub.com)
They are set on the first, second and third floor with lift access and invite you into their large relaxing living areas the minute you walk in. (check-in-london.com)