[1] It is enharmonic equivalent with E♯ (E-sharp)[2] and G (G-double flat),[3] amongst others.
[4] See pitch (music) for a discussion of historical variations in frequency.
E♯ (German: Eis)[5] is a common enharmonic equivalent of F, but is not regarded as the same note.
E♯ is commonly found before F♯ in the same measure in pieces where F♯ is in the key signature, in order to represent a diatonic, rather than a chromatic semitone; writing an F♮ with a following F♯ is regarded as a chromatic alteration of one scale degree.
Though E♯ and F♮ sound the same in any 12-tone temperament, other tunings may define them as distinct pitches.