# Central Kurdish Text-to-Speech Synthesis with Novel End-to-End Transformer Training
## Appendix A  
### Kurdish Language  
This section covers the three major Kurdish dialects and provides an extensive elaboration on the writing system of the Central Kurdish dialect. It also delves into the various pronunciation points and grammatical structure of the language. Most Kurds living in Iraq and Iran use the Central Kurdish dialect. It became an official language of Iraq in 2006. The Northern Kurdish dialect, on the other hand, is commonly spoken in areas such as Syria, Turkey, and Northwestern Iran, among others. Southern Kurdish is also known as Zazaki or Hawrami, and it can be heard in areas such as Ilam and Kermanshah in Iran. The main types of Kurdish are Central and Northern Kurdish, which are, respectively, written in the Latin and Arabic alphabets.  
Despite the number of speakers, the number of resources for the Central Kurdish dialect is still more than sufficient. The system for writing the language was first established during the 1920s, and it has undergone numerous changes. Table A1 provides a brief overview of the phonological features of the phonetic alphabet system.  
The writing system of Central Kurdish is similar to that of a phonemic system. The assigned letter of the language is referred to as a \"phoneme\". Some exceptions are made. For example, the letter \"\(\mathbf{\mathcal{S}}\)\" is pronounced as palatal approximants \"/j/\", and the \"/i/\" as it is referred to as a \"vowel\". The letter \"\(\mathbf{\mathcal{S}}\)\" is also called a bilabial approximant, and it is pronounced as a a vowel: \"/u/\" or \"/v/\". The letter \"\(\mathbf{\mathcal{S}}\)\" can be written in a repetitive way, \"\(\mathbf{\mathcal{S}}\)\", which is pronounced as \"/u/\", a long vowel. Although it is one phoneme, it is not considered as a separate character in the keyboard layout released by the Department of Information Technology of the Regional Government of Kurdistan in 2014.  
Although the Central Kurdish system is similar to that of Persian and Arabic writing, there are differences. Table A2 illustrates the differences between the three alphabets, as they can be used to distinguish among different languages. In Arabic and Persian, there are usually problems with the homograph and Kasre, but in Kurdish writing, these issues do not occur, unlike in other languages, such as Arabic, Persian, and English. Due to the mapping between the written and spoken terms, these issues are not as common.  
Speech synthesis is a multidisciplinary field that has a wide range of problems. Among these is the issue with the management of unfamiliar words, as well as the prosody of proper nouns and foreign ones. In addition, synthesizers commonly encounter issues with the wave concatenation technique due to the varying effects of contextual and thematic factors [41].  
It can be very challenging to create text due to the various language-related aspects involved. For instance, every non-standard term should have a phonetic equivalent. In addition, full words should be made from numbers and letters [42].  
In Central Kurdish, some of the issues that can be encountered are hidden short-vowel characters. For instance, the words (>>_, <>_, <>_, <>_) include hidden short vowels between consonant letters [43].  
In contrast to other languages, such as Persian, English, and Arabic, the problems encountered by speech synthesizer users in Kurdish are not as common. Speech synthesizer users have to recognize the prosodic elements of written text, including the intonation, stress, and length. The features of continuous speech are influenced by the personality and emotions of the artist. Unfortunately, there is a lack of knowledge regarding the prosodic elements in written texts, which causes many of them to be frequently modified as speech is synthesized.