This is the 2432nd most frequent Korean word.
나이가
"Age."
In this sentence, '나이가' describes the quantity or characteristic of age in reference to the person mentioned.
그는 나이가 많아 보여요.
He looks old.
In this sentence, '나이가' refers to the age of the person being asked. It is the subject of the sentence.
나이가 몇 살이세요?
How old are you?
Here, '나이가' is used to imply the advancing age and its effects, functioning as the set topic.