Explanation
-아/야 attaches to a name or noun to call that person: -아 after a consonant (지민아), -야 after a vowel (수지야, 얘야). It is 반말, used down or between close friends and family, so it never goes on a title or an elder's name; there -님 or 씨 plus a plain call does the work. 시영아, 밥 먹자. — Si-yeong, let's eat.