This is the 384th most frequent Korean word.
적이
The Korean word "적이" means "once" or "ever" in the context of describing past experience.
In this sentence, '적이' refers to an instance or occasion.
나는 여기에 온 적이 있다.
I have been here before.
Here, '적이' signifies a past experience.
그는 전쟁에서 싸운 적이 있다.
He has fought in a war.
In this context, '적이' is used to deny a past occurrence.