Latin intervallum space between ramparts, interval, from inter- + vallum rampart. Intervals describe the distance of two tones.
Pure, Minor and Major Intervals
We differentiate pure and minor / major intervals.
Unison, Fourth, Fifth and Octave. These intervals are in the basic form pure intervals.
Minor / Major Intervals
Second, Third, Sixth and Seventh. These intervals appear in two basic forms.
Pure and minor intervals are diminished by lowering the above tone or by heightening the lower tone.
Pure and major intervals are augmented by heightening the above tone or lowering the lower tone.
Consonant and Dissonant Intervals
Melodious intervals are denoted as consonant intervals.
Unison, Octave, Fifth, Fourth, Major and Minor Third.
These intervals sound chafing, odd and disharmonious. Minor Second, Major Second, Diminished Fifth, Augmented Fifth, Seventh