Definition of: diesis

(di′ə·sis) noun
1. Music The difference in tone between a major and a minor semitone, represented by the ratio of vibrations 125:128; also, an interval smaller than a half-step.
2. In Greek music, one of several intervals varying from a semitone to a quartertone.
3. Printing The double dagger (‡): a reference mark for the third in a series. [<L <Gk. <diïenai <dia- through + hienai send]