Is exist a synonyms or a antonyms?

Answer 1

I think you don't understand what a synonym or an antonym is. A synonym is a word that means the same or a similar thing to another word, while an antonym means the opposite. So exist is both a synonym and an antonym, depending on which word you are relating it to. Exist is a synonym for live, but exist is an antonym for, say, in a sense, the word void.