- chrisviana March 2017
We use 은/는 when we don't have any interests about others.
We use 이/가 when we have interests in the relations with others.
For example, Tom은 학생이다 means Tom is "a student". We don't care about if the others are students or not. However, Tom이 학생이다 means a student is "Tom". We use the sentence because we want to know who is a student.
Another example, Sally는 17살이다 means just Sally is "17" simply, but Sally가 17살이다 means "Sally" is 17.
Briefly, we use 이/가 to express who or which one from others.
subject ending in the sentence, we add 이/가. it depend on finish vowel or consonent. 은/는 is very similar with 이/가. but 은/는 we use, 1.when introduce yourself. 2. first sentence use 이/가 second sentrnce use 은/는. 3. generar sentence use 이/가 but compare someting in the sentence use 은/는 4. info focus front use 이/가 info focus back use 은/는 in the sentence.