Diatonic
Proceeding in the order of the octave based on five whole tones and two semitones. The major and natural minor scales and the modes are all diatonic In the major scale, the semitones fall between the third and fourth tones and the seventh and eighth tones. In the minor scale, the semitones fall between the second and third tones and the fifth and sixth tones.
Whole Tone
An interval consisting of two semitones, that is a whole step.
Semitone
A half step; a minor second; the smallest interval in the system of Western music.
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.
Minor
A series of notes that is "natural" or melodic in nature (see Modes & Scales).
The natural minor scale has the same tones as the major scale, but uses the sixth tone of the major scale as its tonic. Thus, the semitones (half steps) are between the second and third tones and the fifth and sixth tones, e.g.:
C, D, E-flat, F, G, A-flat, B-flat, C (ascending)
C, B-flat, A-flat, G, F, E-flat, D, C (descending)
Mode
A series of notes into which the octave is divided according to specific systems. These systems or modes are used as the basis for composing music. The major and minor scales are modes, as well as the gypsy scale, the Gregorian modes, rhythmic modes, etc.