Cyrillization

A Cyrillization is a system for rendering words of a language that normally uses a writing system other than the Cyrillic script into (a version of) the Cyrillic alphabet. A Cyrillization scheme needs to be applied, for example, to transcribe names of German, Chinese, or American people and places for use in Russian, Ukrainian, Serbian, Macedonian or Bulgarian newspapers and books. Cyrillization is analogous to romanization, when words from a non-Latin-script-using language are rendered in the Latin alphabet for use e.g. in English, German, or Francophone literature.

Just as with various Romanization schemes, each Cyrillization system has its own set of rules, depending on:

When the source language uses a fairly phonetic spelling system, a Cyrillization scheme may often be adopted that almost amounts to a transliteration, i.e. using a mapping scheme that simply maps each letter of the source alphabet to some letter of the destination alphabet, sometimes augmented by position-based rules. Among such schemes are several schemes universally accepted in Eastern Slavic languages:

Similarly simple schemes are widely used to render Spanish, Italian, etc. words into Russian, Ukrainian, etc.

When the source language uses a not particularly phonetic writing system—most notably English and French—its words are typically rendered in Russian, Ukrainian or other Cyrillic-based languages using an approximate phonetic transliteration system, which aims to allow the Russian, Ukrainian, Bulgarian, etc. readers to approximate the sound of the source language as much as it is possible within the constraints of the destination language and its alphabet. Among the examples are the Practical transcription of English into Russian (Russian: Правила англо-русской практической транскрипции), which aims to render English words into Russian based on their sounds, and Transliteration of foreign words by a Cyrillic alphabet () and Cyrillization of the English language () in the case of Ukrainian. While this scheme is mostly accepted by a majority of Russian and Ukrainian authors and publishers, transcription variants are not uncommon.

...
Wikipedia