Daijoubu is a very versatile word in Japanese that generally means “I’m (or it’s) okay“. I say versatile because it can act both as a positive or negative confirmation depending on the situation.
For example, if you accidentally tripped and fell, your friend will ask you “daijoubu (are you okay)?” If you’re not hurt and totally fine, you can positively confirm to them saying “daijoubu (I’m okay)”.
On the other hand, if a server asks if you would like your water refilled while dining at a restaurant and you don’t need it, you can negatively confirm by saying “daijoubu desu”, which in this case means something like “no, thank you”.
Versatile, right??