The antonyms for the word "cooccur" are "occur" and "non-occur". "Occur" means to take place or happen, whereas "cooccur" means to happen simultaneously or together. Therefore, if two events do not occur at the same time, they are opposite of "cooccur". On the other hand, "non-occur" means that something does not happen at all. For example, if it is said that an event occurred, but it did not "cooccur" with another event, it means that the two events happened at different times. Similarly, if an event never happens, it is said to "non-occur". The use of antonyms allows us to clarify the meaning of a word and convey the proper message.