0 used to mean the thing, situation, or idea that has already been talked about -- 그것
1 used before some adjectives, nouns, or verbs to introduce an opinion or description of a situation -- 상황 설명이나 의견을 말할 때 쓴다
2 used with a verb in sentences giving the time, date, weather, or distances -- 시간, 날짜, 날씨, 거리등을 말할때 쓴다
3 used to say the name of a person or thing when the person you are speaking to does not know -- 사람을 가리켜 쓰인다
4 the use of computers and other electronic equipment to keep and send information -- 아이티, 정보 통신 기술