Korean culture, in general, is more polite and formal than what you might be used to. Use polite, formal language out in public, such as when you’re thanking a shopkeeper, server, or sales clerk.
If you’re talking to friends with whom you’d normally speak more informally, the politeness of this phrase can communicate more sincere gratitude. You might use it, for example, when thanking a friend for going out of their way to help you with something serious or important.
To refuse an offer from someone familiar to you, but with whom you should still be polite (such as an older relative or other adult), say 아니요 괜찮아요 (a-ni-yo gwaen-chan-a-yo). If you want to say “no, thank you” to someone your age or younger who you’re on familiar terms with, say 아니 괜찮아 (a-ni gwaen-chan-a). Never use this phrase with strangers or people older than you, even if you’re close to them – it will be considered rude.
If you use 고마워요 (go-ma-weo-yo) with people you don’t know, this polite phrase suddenly becomes rude. If you’re not sure if it would be okay to use this phrase, use one of the formal expressions of gratitude instead.
Avoid using this phrase to say “thank you” to anyone you don’t know, even if they’re considerably younger than you, unless they are small children. Casual Korean is never used between adults who are strangers, even if there is a significant age gap between you.
You can add 정말 (jeong-mal) to the beginning of formal expressions of gratitude as well. For example, if you lost your passport in a restaurant and a server helped you find it, you might say 정말 고마워요 (jeong-mal go-ma-weo-yo) to them. You can also add 정말 (jeong-mal) to be more emphatic about turning down something offered to you. For example, you might say 아니요 정말 괜찮아요 (a-ni-yo jeong-mal gwaen-chan-a-yo). In context, it’s a bit like saying “No really, it’s okay, thank you” or “Thank you very much, but no” in English.
아니에요 (a-ni-ae-yo) is the polite form, but is appropriate in most situations. If you need to be more formal, such as if you’re responding to someone older than you or in a position of authority, use 아닙니다 (ah-nip-nee-da).
This phrase is typically taken to mean that thanks aren’t necessary – you were glad to do whatever it was you did or it was no trouble for you. There isn’t a more formal form of this particular phrase, so you might not want to use it if you are talking to someone significantly older than you or someone in a position of authority. You might come off as rude.
괜찮아요 (gwen-chan-ah-yo) is the polite form. If you need to be more formal, such as with an adult you don’t know or a person in a position of authority, use 괜찮습니다 (gwen-chan-seup-nee-da).
