나

In a sentence

• 나는 책을 읽고 있어.

  I am reading a book.

  Here, '나' is used as the first-person singular pronoun in its subject form, as 'I', combined with the subject particle '는'.

• 이건 내가 필요해.

  I need this.

  In this sentence, '나' is used as the first-person singular pronoun in its informal possessive/subjective form, combined with the subject particle '가' as '내가'.

• 친구들은 나를 좋아해.

  My friends like me.

  Here, '나' functions as 'me' or the object in the sentence, pairing with the object particle '를' to form '나를'.