Leading Note
Also called "leading tone"; the major seventh of a scale, so called because it lies a semitone below the tonic and "leads" towards it.
Major
Term referring to a sequence of notes that define the tonality of the major scale. This series consists of seven notes: the tonic, followed by the next note a whole step up from the tonic, the third is a whole step from the second, the fourth is a half step from the third, the fifth is a whole step from the fourth, the sixth is a whole step from the fifth, the seventh is another whole step, followed by the tonic, a half step above the seventh. Thus the first and eighth tones are exactly an octave apart.
Seventh
An interval that is one step smaller than an octave. A major seventh is a semitone smaller than an octave, and a minor seventh is a whole tone smaller than an octave.
Semitone
A half step; a minor second; the smallest interval in the system of Western music.