How to Say "Informal Thank You" in Korean

고마워

gomawo[ko̞ma̠wʌ̹]

The Korean phrase for an informal thank you is 고마워 (gomawo).

고마워 is a casual way to express gratitude to a friend or someone younger.

Which one should you use?

While 고마워 is used for close friends or younger people, the more formal/polite version is 고마워요 or the even more formal 감사합니다.

Adding the suffix –요 to the end of 고마워 makes it a polite form suitable for people you are not close with or are older than you.

gomawo

The root of 고마워, 고맙다, is an ancient Korean word that is believed to be related to the concept of 'spirit' or 'divinity' in some linguistic theories. This suggests that expressing thanks originally had a much deeper, almost sacred, connotation than a simple social courtesy.
In Korean culture, your choice of words matters more than your intention. Even if you use 고마워 with a friendly smile, saying it to a person older than you or of a higher social status can be seen as a significant social transgression rather than a simple slip of the tongue.
If you are texting a close friend, you might see 고마워 shortened even further to just 고마 or written with extra vowels like 고마웡 to sound 'cute' or 'aegyo'.

선물 정말 고마워.
seonmul jeongmal gomawo.
Thank you so much for the gift.
도와줘서 고마워.
dowajwoseo gomawo.
Thank you for helping me.
맛있는 거 사줘서 고마워.
masinneun geo sajwoseo gomawo.
Thank you for buying me something delicious.

Two friends are at a cafe after a study session.

수빈 Su-bin

커피 사줘서 고마워, 도현아.
keopi sajwoseo gomawo, dohyeona.
Thank you for buying me coffee, Dohyeon.
도현 Do-hyeon

아니야, 별거 아니야.
aniya, byeolgeo aniya.
No problem, it's nothing.
수빈 Su-bin

진짜 잘 마실게!
jinjja jal masilge!
I will really enjoy it!
도현 Do-hyeon

그래, 맛있게 마셔.
geurae, masitge masyeo.
Sure, enjoy your drink.

Sources

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