Gomennasai Versus Sumimasen in Japanese

Both "Gomennasai" and "Sumimasen" are used when you have made a mistake or inconvenienced someone. "Sumimasen" is also used when expressing a feeling of gratitude, but "Gomennasai" cannot be used in such situations.

For the most part, it comes down to a matter of personal preference whether to use either "Sumimasen （すみません）" or "Gomennasai （ごめんなさい）", but there are a few subtleties to be aware of.

• "Sumimasen" is a little more formal than "Gomennasai."
• When you apologize to the higher or the senior, "Sumimasen" is used in general.
• Among the family members or close friends, it is common to use "Gomennasai." "Gomen ne" or "Gomen" can be used in a more casual case.
• Older people tend to use "Sumimasen" more than younger people.

"Gomennasai" can be used when apologizing to someone with whom you have a close relationship. But when speaking with superiors or people with whom one is not very close, "Sumimasen" or "Moushiwake arimasen" are used instead, since "Gomennasi" can have a childish ring to it.