The specific letters used will depend on the alphabet of the language the word comes from. Some examples include:
* Latin alphabet: Used in English, Spanish, French, German, etc.
* Cyrillic alphabet: Used in Russian, Ukrainian, Bulgarian, etc.
* Greek alphabet: Used in Greek, of course!
* Arabic alphabet: Used in Arabic, Persian, Urdu, etc.
* Japanese writing system: Uses three different scripts: hiragana, katakana, and kanji (borrowed Chinese characters).
So, while foreign words might look different because of the alphabet they use, they're still fundamentally composed of letters!