Gaj's Latin alphabet (, ), also known as (, ) or (, ), is the form of the Latin script used for writing Serbo-Croatian and all of its standard varieties: Bosnian, Croatian, Montenegrin, and Serbian. The alphabet was initially devised by Croatian linguist Ljudevit Gaj in 1835 during the Illyrian movement in ethnically Croatian parts of Austrian Empire. It was largely based on Jan Hus's Czech alphabet and was meant to serve as a unified orthography for three Croat-populated kingdoms within the Austrian Empire at the time, namely Croatia, Dalmatia and Slavonia, and their three dialect groups, Kajkavian, Chakavian and Shtokavian, which historically utilized different spelling rules. A slightly modified version of it was later adopted as the formal Latin writing system for the unified Serbo-Croatian standard language per the Vienna Literary Agreement. It served as one of the official scripts in the unified South Slavic state of Yugoslavia alongside Vuk's Cyrillic alphabet. A slightly reduced version is used as the alphabet for Slovene, and a slightly expanded version is used as the alphabet for modern standard Montenegrin. A modified version is used for the romanization of Macedonian. It further influenced alphabets of Romani languages that are spoken in Southeast Europe, namely Vlax and Balkan Romani. Letters The alphabet consists of thirty upper and lower case letters: Gaj's original alphabet contained the digraph , which Serbian linguist Đuro Daničić later replaced with the letter . The letters do not have names, and consonants are normally pronounced as such when spelling is necessary (or followed by a short schwa, e.g. ). When clarity is needed, they are pronounced similar to the German alphabet: a, be, ce, če, će, de, dže, đe, e, ef, ge, ha, i, je, ka, el, elj, em, en, enj, o, pe, er, es, eš, te, u, ve, ze, že. These rules for pronunciation of individual letters are common as far as the 22 letters that match the ISO basic Latin alphabet are concerned. The use of others is mostly limited to the context of linguistics, while in mathematics, is commonly pronounced jot, as in the German of Germany. The missing four letters are pronounced as follows: as ku or kju, as dublve, duplo v or duplo ve, as iks, as ipsilon. Letters , , and represent the sounds , , and , but often are transcribed as , , and . Digraphs Digraphs , and are considered