noun
The letter F itself, used as a symbol, grade, or label.
成績表にFがついていた。
There was an F on my report card.
suffix
floor number
Only when written F
Suffix attached to a number to indicate a floor in a building, e.g., 1F = first floor. Restricted to the uppercase form F.
受付は2Fにあります。
The reception desk is on the 2nd floor.