third
musical interval encompassing three staff positions; either a major third (four semitones) or a minor third (three semitones) in diatonic scales
minor third
musical interval encompassing three staff positions and three semitones
diminished third
musical interval
augmented third
musical interval of five semitones spanning three staff positions (e.g. from C to E♯); enharmonically equivalent to the perfect fourth
neutral third
any interval wider than a minor third but narrower than a major third, e.g. with frequency ratios of 11:9 (undecimal neutral third), 16:13 (tridecimal neutral third) or with exactly 3½ semitones in equal temperament (equal-tempered neutral third)
major third
musical interval encompassing three staff positions and four semitones, with a frequency ratio of approximately 5:4=1.25 (∛2 = 1.260… in equal temperament)