Transliteration is the transformation of text from one script (writing system) to another. This is also referred to as transcription.
There are no single standard transliteration mappings between any script and any other script. Where a transliteration mapping exists in a language, such as Pinyin in China, an alternative system exists elsewhere, as in Taiwan. Greek from Greece may be transliterated differently from Greek from , and so on.
Text can be transliterated in many different ways according to source and also target language. For example, GIANNHS (meaning John) in Greek may be transliterated into Yanis or Yannis in English because that's what it sounds like (orthographic bias transliteration); but by the same token it may be Jannis in German. If the language into which the transliteration is being made has multiple ways of producing the sound in the source language, these variations will be found in trasliterations.
As languages often do not share the same sound, compromises made during phonetic transliteration can cause differences between transliterated versions.
Transliteration may be carried out letter-by-letter instead of by sound, but as alphabets in each language differ, this also leads to variation.
Transliterations of Muamar Ghaddafi in a mathematical formulation. Source: Wikipedia
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