diesis

• A diesis is a quarter tone; hence in a semitone there are included two dieses. —  The Ten Books on Architecture
• The fraction, 64/125, representing a longer segment of the string than 64/128 (1/2), it would produce a flatter tone than the exact half It is evident, therefore, that all major thirds must be tuned somewhat sharper than perfect in a system of equal temperament The ratio which expresses the value of the diesis is that of 128 to 125. —  Piano Tuning A Simple and Accurate Method for Amateurs
• _Otello_ at the Théâtre-Italien, but that was to hear Tamberlick's C diesis. —  Musical Memories
• _The Marks_ *, [obelus], [diesis], _&c. —  Notes and Queries, Number 59, December 14, 1850
• Therefore our proficiency is limited to these few words; but beyond them it does not exist even in the slightest degree WHAT THE BEGINNING OF PHILOSOPHY IS.--The beginning of philosophy, to him at least who enters on it in the right way and by the door is a consciousness of his own weakness and inability about necessary things; for we come into the world with no natural notion of a right-angled triangle, or of a diesis (a quarter tone), or of a half-tone; but we learn each of these things by a certain transmission according to art; and for this reason those who do not know them do not think that they know them. —  A Selection from the Discourses of Epictetus with the Encheiridion

Allen's Synonyms and Antonyms