How to Say "Thank You" in Japanese, Formal, Informal and Casually

The least formal, casual way of saying “thanks” is “duomo,” which is used when speaking to a close friend or peer. A more polite way of saying “thank you” in Japanese is “arigatou.” You would use “arigatou” if you were thanking an acquaintance or someone you don’t know all that well. To say “thank you very much,” you would say “duomo arigatou.” A more formal way of saying thank you is “arigato gozaimasu.” Use “arigato gozaimasu” when speaking to elders, teachers, in business situations or with those who command your respect. To say “thank you very much” in this same polite form, combine the casual “thanks” with the polite form of thank you and say “duomo arigatou gozaimasu.”

“Arigatou gozaimashita” is the past tense form of the polite thank you and is used when someone has given you something that you want to thank him for. Use “arigatou gozaimashita” to express thanks to a teacher, or to a hostess when leaving a party.

“Sumimasen” is another way to say “thank you” in Japanese. This translates also into an apology, as in saying you’re sorry for troubling someone, or thanking her for going out of her way to help you. It is formal and not something you would use with a close buddy. “Osoreirimasu” is the most formal form of saying thank you. "Osoreirimasu" acknowledges someone for her time and effort in your behalf and is most often used in business or with strangers you want to impress.