A diatonic semitone, minor second or limma is the small step of a diatonic scale.
In just intonation, an interval may be classified as a diatonic semitone if it is reasonably mapped to 1\7 and 2\24 (precisely one step of the diatonic scale and one step of the chromatic scale). Do note that 24edo's 2\24 is used as the mapping criteria here rather than 12edo's 1\12 since 12edo tempers out certain intervals that otherwise qualify as diatonic semitones.
- 256/243, the Pythagorean diatonic semitone (3-limit)
- 16/15, the classic diatonic semitone (5-limit)
- 128/121, the Axirabian diatonic semitone (11-limit; specifically belonging to the 2.3.11 subgroup)