their modern pronunciation as ypogegrammeni and prosgegrammeni respectively, were also chosen for use in character names in the computer encoding standard Unicode. As a phonological phenomenon, the original diphthongs denoted by are traditionally called "long diphthongs". They existed in the Greek language up into the classical period. From the classical period onwards, they changed to simple vowels (monophthongs), but sometimes continued to be written as diphthongs. In the medieval period, these spellings were replaced by spellings with an iota subscript, to mark former diphthongs which were no longer pronounced. In some English works these are referred to as "improper diphthongs". Usage The iota subscript occurs most frequently in certain inflectional affixes of ancient Greek, especially in the dative endings of many nominal forms (e.g. ) as well as in certain verb forms of the subjunctive mood (e.g. ). Besides these it also occurs in the roots of certain words and names, for instance , ode (and its derivatives: , odeon; , tragedy etc.); , Hades; , Thrace. The rare long diphthong might logically have been treated the same way, and the works of Eustathius of Thessalonica provide an instance of with iota subscript (in the word ), but this never became the convention (the same word being spelled by other writers as or ). The iota subscript is today considered an obligatory feature in the spelling of ancient Greek, but its usage is subject to some variation. In some modern editions of classical texts, the original pronunciation of long diphthongs is represented by the use of iota adscript, with accents and breathing marks placed on the first vowel. The same is generally true for works dealing with epigraphy, paleography or other philological contexts where adherence to original historical spellings and linguistic correctness is considered important. Different conventions exist for the treatment of subscript/adscript iota with uppercase letters. In Western printing, the most common practice is to use subscript diacritics only in lowercase environments and to use an adscript (i.e. a normal full-sized iota glyph) instead whenever the host letter is capitalized. When this happens in a mixed-case spelling environment (i.e. with only the first letter of a word capitalized, as in proper names and at the beginning of a sentence), then the adscript iota regularly takes the shape of the normal lowercase iota letter (e.g. → ). In an all-capitals environment, the adscript is also regularly capitalized (). In Greece,