The interval which encompasses 5 degrees of a diatonic scale. It is usually close in size to the frequency ratio 3:2, which is approximately 702 cents.
In the usual 12-EDO tuning, the perfect 5th encompasses 7 semitones, and is thus exactly 700 cents.
Here is a graph of the size of the best approximation to the "5th" in cents, for all the EDOs from 10 to 72:
[from Joe Monzo, JustMusic: A New Harmony]
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The interval 3/2 in Just Intonation or the closest approximation to 702 cents (¢) in an equal temperament.
The Diapente in Greek.
[from John Chalmers, Divisions of the Tetrachord]
