Enharmonic
A pitch can be notated, or spelled, in more than one way. This is easily demonstrated on a keyboard. Accidentals are used to move a note up or down by a half step or two. For example, an F sharp is the same note as a G flat. It is the black key between the F and the G. If you proceed down a half step from C to C flat, that note is also called B natural. Likewise, E sharp is the same as F natural, spelled enharmonically. This illustrates that flats and sharps can be white keys on the keyboard. F flat is the same pitch as D double sharp, and E natural. Enharmonic spellings occur whenever a pitch is notated by a different name than would be ordinarily used in a given key.