1f or F 
/ˈɛf/ noun
plural f's or fs or F's or Fs /ˈɛfs/ /ˈɛf/ noun 1 : the sixth letter of the English alphabet [count] ▪ The word “foot” begins with an f. [noncount] ▪ The word “foot” begins with f. 2 : a musical note or key referred to by the letter F : the fourth tone of a C-major scale [count] ▪ play/sing an F [noncount] ▪ the key of F 3 [count] : a grade that is given to a student who is doing very poor work
▪ I got an F on the test.
▪ I got an F on the test.
