Romance Languages:
* Spanish: Agradecido/a
* French: Reconnaissant(e)
* Italian: Grato/a
* Portuguese: Grato/a
* Romanian: Recunoscător/recunoscătoare
Germanic Languages:
* German: Dankbar
* Dutch: Dankbaar
* Swedish: Tacksam
* Norwegian: Takknemlig
* Danish: Taknemmelig
Slavic Languages:
* Russian: Благодарный (blagodarnyy)
* Polish: Wdzięczny
* Czech: Vděčný
* Ukrainian: Вдячний (vdyachnyy)
Other Languages:
* Chinese (Mandarin): 感激 (gǎnjī)
* Japanese: 感謝 (kansha)
* Korean: 감사 (gamsaha)
* Arabic: شاكر (shakir)
* Hindi: आभारी (aabhāri)
* Vietnamese: Biết ơn
This is not an exhaustive list, and there may be other ways to express "thankful" depending on the context and nuance.