Polite : 제 거예요. [je geoyeyo] 제 (my) = 저 (I, me) + 의 (possessive particle) 거예요 = 거 (thing) + 예요 (to be) Informal : 내 거야. [nae geoya] 내 (my) = 나 (I, me) + 의 (possessive particle) 거야 = 거 (thing) + 야 (to be) This literally translates to "It's my thing", that's just how Koreans say it. Note that although 거 is normally pronounced [geo], in this expression you have to pronounce it as 꺼 [kkeo]. :)