This is the 104th most frequent Korean word.
아닌
"Not" or "not being."
'아닌' is used to negate the phrase it is describing, indicating that the statement is not true.
나는 그 말이 진실이 아닌 것 같아.
I think that the statement does not seem to be true.
'아닌' negates '내 잘못', indicating that the situation was not the speaker's fault.
그것은 내 잘못이 아닌, 단순한 오해였다.
It was not my fault; it was merely a misunderstanding.
'아닌' is used to negate '내가 찾던 것', suggesting that the object is not what the speaker was seeking.