이다 vs 있다 You can think of English's "be" and its Korean counterparts as the following three cases: 1) AA is BB. (where BB is a noun or a noun phrase) => 이다. (I am a student = 나는 학생이다) 2) AA is (adjective). => no special word. (I am sad = 나는 슬프다. No 이다 needed) 3) AA is. /There is AA. => 있다. (I am at school = 나는 학교에 있다. There is a car = 차가 있다) 이다 always couples two substantives and in no other sense, but sometimes it can appear obscure because it can take many different forms (이다, 입니다, 이야, 이에요, 예요), always attaching to a noun directly without a space, and because it is very often contracted and sometimes even left out. 있다 is "is" in the sense of "exist", but it can also be used like "have", since having something means something exists in your possession. Examples: - 그는 위대한 사람이다 => He is a great man. - 이것이 우리가 해야 할 일입니다/일이다 => This is what we need to do. - 지는 것이 이기는 거야 => To lose is to win. (거야 is short for 것이야, which has 이다 in it) - 분모가 10이면 분자는 5다 => If the denominator is 10, the numerator is 5. (both 10이면 and 5다 have 이다 in them) - 세상은 넓다 => The world is big. (neither 이다 nor 있다 is necessary - Korean adjectives don't required 이다다) - 길 건너편에는 학교가 있다 => There is a school on the other side of the street. - 옛날에 한 소녀가 있었다 => Once upon a time there was a girl. (있다 in the past tense) - 나한테 돈이 50만 원 있어 => I have 500,000 Won on me (There is 500,000 Won in my possession) If any part is unclear, please ask again.