ISO 9

The ISO international standard ISO 9 establishes a system for the transliteration into Latin characters of Cyrillic characters constituting the alphabets of many Slavic and non-Slavic languages.

The major advantage ISO 9 has over other competing systems is its univocal system of one character for one character equivalents (by the use of diacritics), which faithfully represents the original spelling and allows for reverse transliteration, even if the language is unknown.

Earlier versions of the standard, ISO/R 9:1954, ISO/R 9:1968 and ISO 9:1986, were more closely based on the international scholarly system for linguistics (scientific transliteration), but have diverged in favour of unambiguous transliteration over phonemic representation. The edition of 1995 supersedes the edition of 1986.

ISO 9:1995, or GOST 7.79 System A

The standard features three mapping tables: the first covers contemporary Slavic languages, the second older Slavic orthographies (excluding letters from the first), and the third non-Slavic languages (including most letters from the first). Several Cyrillic characters included in ISO 9 are not available as precomposed characters in Unicode, neither are some of the transliterations; combining diacritical marks have to be used in these cases. Unicode, on the other hand, includes some historic characters that are not dealt with in ISO 9.