In English demonstratives would be words like ‘this’, ‘that’, or ‘over there’. In Korean, the demonstrative prefix for ‘this’ is 이, that = 그, that over there = 저. To be more specific, 이것 is used when the object is close to the speaker. Therefore a sentence like 이것은 제 책이에요 would mean that the 책 is near the speaker. (이것 = this [object]. 은 = topic marking particle. 제 = ‘my’ polite form. 책 = book. 이에요 = copula meaning ‘is’ in the standard polite form.) In English this sentence would mean, ‘This is my book’. 그것 would mean that the book is far away from the speaker and close to the listener.

Therefore, if you replace 이것 with 그것 and keep everything in the sentence above, you get, 그것은 제 책이에요. The sentence would now mean, ‘That is my book’. Now change 그것 with 저것. The sentence would now be 저것은 제 책이에요. This time the sentence would mean, ‘That book over there is my book.’ 저것 is used for objects that are far away from both the speaker and the listener. Someone once asked me, what demonstrative would you use if the book is of equal distance between the speaker and the listener? I guess in this case you’ll have to use your subjective judgement as to whether to use ‘this’ or ‘that’.

When you use the topic marking particle 은 with any demonstrative, Korean people tend to contract these forms. So ‘this, that, over there’ will be 이건, 그건, 저건 respectively. Using the sentence above, 이것은 제 책이에요 will be 이건 제 책이에요. You can use the contracted forms for both 그것 and 저것 as well. There is also a contraction when you use the subject marking particle 이 with these demonstratives. The non contracted forms would be 이것이, 그것이, 저것이. The contracted forms would be 이게, 그게, 저게. For the sake of saving time and ease of pronunciation, the contracted forms are preferred over the non contracted forms.

Notice that in English the sentence ‘this is my book’ would mean the same whether the sentence was 이것이 제 책이에요 or 이게 제 책이에요. The same goes for 이것은 제 책이에요 and 이건 제 책이에요. This is where Korean proves to have subtler nuances in a simple sentence like ‘this is my book’. Also, the demonstrative prefixes 이, 그 and 저 can be used to refer to people as well. 이분, 그분 and 저분 respectively mean this person, that person and that person over there. So you could say, 이분 알아요? Or, ”do you know this person?” (이분 = this person. 알아요 = verb to ‘know’ in the standard polite form.)