The Subject of a Sentence in Korean—Usage of Josa for Nominative Case 주격조사(josa for nominative(subjective) case) signifies the subject of a sentence. Here, I'm going to explain the usage of 주격조사('이, 가, 에서, 께서') In the nominative case(subjective case), there are 가(if there's Korean consonant at the lower part of a syllable '이' is used instead of '가'), 께서(it's used for honorific language), and '에서'. '이', '가', '께서' is used for animate noun. '대성이가' 아픈가 봐. (Daeseong seems sick.) '가' is josa for nominative case, but '이' is not. '이' was used as suffix between the name '대성' and '가' for phonemic reason since there is 받침 ㅇ(Korean consonant placed at the lower part of syllable '성'). '상급반 학생들이' 학교 앞 청소를 한다. (Senior class students are cleaning in front of school.) '강아지가' 깡충깡충 뛰어 다닌다. (The puppy is hopping around.) '에서' in che-eon modifying clause[관형절] '정부에서 실시한' signifies '정부' is the subject of the clause. Josa '가' was used for '정부에서 실시한 설문조사 결과' is the subject of the sentence. 마라톤 개막식에서 '시장님께서' 춤을 추고 계셨다 . (The city mayor was dancing in the marathon opening ceremony.) '에서' as in 개막식 is josa for adverbial case[부사격조사]; it signifies preceding word performs as the adverb representing the place(마라톤 개막식). Unlike other josas for nominative case, '에서' is used for inanimate nouns. 1.'평창에서' 2018년에 동계 올림픽을 연대. (Pyeongchang holds Winter Olympics in 2018.) 2.이번 전국치어리딩대회는 '우리 학교에서' 우승을 차지했다.(My school won the championship in national cheerleading competition. I didn't translate '우리' literally because of some regional cultural viewpoint. For reference, '우리' is preferred instead of '나의' in some cases) 3.'우리 회사에서' 새로운 디자인의 자동차를 개발하였다. (My company has developed a new-design-car) '에서' in '평창에서', '우리 학교에서' was used for nominative case. However, there are a few conditions when using '에서' as the josa for nominative(subjective) case. 4.'저 축구 팀에서(x)/저 축구 팀이(o)' 참 훌륭하다.(The soccer team is really great.) 5.우리 반에서(x)/우리 반이(o) 가장 우수합니다.(My class is the best. ) It's probable that the reason is that, originally, '에서' wasn't used as the josa for nominative case. If '에서' is used as the josa for the adverbial case indicating a place, 1 and 3 are changed as the following #1 and #3. #1. 평창에서 2018년에 동계 올림픽이 열린대. (The Winter Olympics is held in Pyeongchang in 2018.) #3. 우리 회사에서 새로운 디자인의 자동차가 개발되었다.(The new-design-car has been developed in my company.) As you see, passive verbs 열린대, 개발되었다 were used in #1 and #3. The basic form of 연대, 열린대 is 열다. 열다 takes irregular conjugation of ㄹ. The stem 열- was dropped by combining with ending '-ㄴ대'.