99% of the time if the sentence ends with 요/죠/니다/니까 it's a form 준댓말 If it ends in 아,니,자, it's probably 반말 There are also certain words only used in either For example: I, you, me, my (반말) - 나, 너, 내가, 내 I, you, me, my (준댓말) - 저, 당신, 저(를), 제 A polite way to say I am hungry: 배고파요 A casual way: 배고파 Very easy one!! Hello: 안녕하세요 - polite 존댓말 Hello: 안녕 - casual - 반말