What is the Japanese term for 'thank you'?

The term 'thank you' in Japanese is 'Arigatou.' This word is used to express gratitude and can be used in both casual and polite settings. It is a common phrase that shows appreciation for kind acts or services received from others.

In contrast, the other options serve different functions in the Japanese language. 'O Genki Desu Ka' translates to 'How are you?' and is used to inquire about someone's well-being. 'Itadakimasu' is a phrase uttered before meals, expressing gratitude for the food, akin to saying 'I humbly receive.' 'Sumimasen' can mean 'excuse me' or 'I'm sorry,' and it is used to express regret or to get someone's attention rather than to convey thanks. Understanding these distinctions is crucial for effective communication in Japanese.