Romance Languages:
* Spanish: fiel
* French: fidèle
* Italian: fedele
* Portuguese: fiel
* Romanian: fidel
Germanic Languages:
* German: treu
* Dutch: trouw
* Swedish: trogen
* Danish: tro
* Norwegian: trofast
* English: faithful (of course!)
Slavic Languages:
* Russian: верный (verny)
* Polish: wierny
* Czech: věrný
* Slovak: verný
* Ukrainian: вірний (virny)
Other Languages:
* Arabic: أمين (amin)
* Chinese (Mandarin): 忠诚 (zhōngchéng)
* Japanese: 忠実 (chūjitsu)
* Korean: 충실 (chung-sil)
* Hindi: वफ़ादार (vafadaar)
* Turkish: sadık
* Greek: πιστός (pistos)
Note: Some of these words may have slightly different nuances than "faithful" in English. For example, "verny" in Russian can also mean "true" or "correct."
This is just a small sample of the many languages in the world. If you need a translation for a specific language, I recommend using an online translation tool or consulting a dictionary.