Interordinal
From XenReference
Interordinals (also called interseptimals, which however has certain other senses on this wiki) are interval categories halfway between adjacent interval classes of the diatonic scale. For example, 250c is an interordinal because it falls between 200c (the 12edo major second) and 300c (the 12edo minor third).
19edo and 24edo are notable edos with interordinals. Notable JI interordinals include 15/13 (a semifourth) and 13/10 (a semisixth).
The following table shows various ways to name interordinals:
| 24edo interval | "semi" names | "inter" names | "ultra"/"infra" | Greek-derived names |
|---|---|---|---|---|
| 250c, 5\24 | semifourth | second-inter-third | ultramajor second inframinor third |
chthonic |
| 450c, 9\24 | semisixth | third-inter-fourth | ultramajor third infrafourth |
naiadic |
| 750c, 15\24 | semitenth | fifth-inter-sixth | ultrafifth inframinor sixth |
cocytic |
| 950c, 19\24 | semitwelfth | sixth-inter-seventh | ultramajor sixth inframinor seventh |
ouranic |
