![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/5/53/Syntonic_comma_on_C_HE_notation.png/640px-Syntonic_comma_on_C_HE_notation.png&w=640&q=50)
Syntonic comma
Musical interval / From Wikipedia, the free encyclopedia
In music theory, the syntonic comma, also known as the chromatic diesis, the Didymean comma, the Ptolemaic comma, or the diatonic comma[2] is a small comma type interval between two musical notes, equal to the frequency ratio 81:80 (= 1.0125) (around 21.51 cents). Two notes that differ by this interval would sound different from each other even to untrained ears,[3] but would be close enough that they would be more likely interpreted as out-of-tune versions of the same note than as different notes. The comma is also referred to as a Didymean comma because it is the amount by which Didymus corrected the Pythagorean major third (81:64, around 407.82 cents)[4] to a just major third (5:4, around 386.31 cents).
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/5/53/Just_perfect_fifth_on_D.png/320px-Just_perfect_fifth_on_D.png)
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Major_second_on_C.svg/640px-Major_second_on_C.svg.png)
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/5/5b/Minor_tone_on_C.png/320px-Minor_tone_on_C.png)
The word "comma" came via Latin from Greek κόμμα, from earlier *κοπ-μα = "a thing cut off".