Interordinal
From XenReference
Interordinals 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). Interordinals may sometimes be called interseptimals;, however the term "interseptimal" also has certain other senses on this wiki.
19edo, 24edo, and 29edo are notable edos with a complete set of 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 |
