꼭 (kkok) · 반드시 (ban-deu-si, bandeusi)
꼭 expresses strong personal will or certainty in everyday contexts, while 반드시 conveys a formal, mandatory sense used in strict or official situations.
One lane per word — no nested boxes, just the gist.
An adverb expressing strong will or certainty, commonly used in everyday conversation
When to use
Everyday requests, Strong personal will, Friendly conversation
The nuance
Use 꼭 to emphasize your will or when making requests, giving a natural and friendly tone.
A formal and strict adverb used when something must be done unconditionally or without fail
When to use
Legal requirement, Official instructions, Strict rules
The nuance
Use 반드시 to emphasize legal, official, or strict rules with a sense of obligation.
내일 꼭 학교에 와야 해.
nae-il kkok hak-gyo-e wa-ya hae., nae il kkok hak gyo e wa ya hae.
꼭 naturally expresses strong will or request, suitable for everyday conversation.
내일 반드시 학교에 와야 해.
nae-il ban-deu-si hak-gyo-e wa-ya hae., nae il ban deu si hak gyo e wa ya hae.
반드시 is suitable to emphasize strict rules or promises that must be kept.
꼭 법을 지켜야 한다.
kkok beop-eul ji-kyeo-ya han-da., kkok beop eul ji kyeo ya han da.
When referring to law compliance, 반드시 with its formal and strict nuance must be used.
반드시 친구에게 전화해 줘.
ban-deu-si chin-gu-e-ge jeon-hwa-hae jwo., ban deu si chin gu e ge jeon hwa hae jwo.
For requests to friends, the friendly 꼭 is more natural than 반드시.
시험에 반드시 합격할 거야.
si-heom-e ban-deu-si hap-gyeok-hal geo-ya., si heom e ban deu si hap gyeok hal geo ya.
반드시 is appropriate to emphasize definite results or goals.
시험에 꼭 합격할 거야.
si-heom-e kkok hap-gyeok-hal geo-ya., si heom e kkok hap gyeok hal geo ya.
꼭 naturally expresses strong personal will and hope.
꼭 이 규칙을 따라야 한다.
kkok i gyu-chik-eul tta-ra-ya han-da., kkok i gyu chik eul tta ra ya han da.
Rule compliance requires 반드시’s strict and mandatory nuance.
반드시 부탁을 들어주세요.
ban-deu-si bu-tak-eul deul-eo-ju-se-yo., ban deu si bu tak eul deul eo ju se yo.
꼭 is more suitable for requests; 반드시 sounds unnatural here.
Which is more natural when making a request to a friend?
Which word is appropriate to emphasize legal rules?
Which word can be used to express strong personal will?
