The word "non-existent" refers to something that does not exist or is not present. Its antonyms, or opposite words, include "existent," which means real or actual, and "present," which refers to something that is there or available. Other antonyms for "non-existent" may include "existing," "alive," "existent," "present," "real," "substantial," and "tangible." These words indicate that the object, idea, or thing in question is real, present, and has substance. It is important to know these antonyms as they can help us describe and differentiate between what is present and what is not in various situations.