This is the 754th most frequent Korean word.
하나
"하나" means "one" in English.
Here '하나' is used as the numeral 'one', quantifying the noun '사과' (apple), emphasizing the quantity of items.
나는 사과 하나를 먹었다.
I ate one apple.
In this sentence, '하나' is used to indicate a choice of an individual item from a group, emphasizing the singular selection.
이 중에서 하나를 골라봐.
Pick one among these.
Here, '하나' is used symbolically to convey the concept of unity or being 'one' as a whole.