Semitone

A semitone is a half tone step. On the piano, this is often black-to-white or white-to-black (except for 2 places where they're both white).

Some examples:

• C > C#
• Bb > B
• E > F

Sheet music will add accidentals sometimes to show semitones not in the key signature - eg: the opening notes of Für Elise

A chromatic scale is made from entirely semitones.

Also see Intervals