Nonidentical refers to things that are not the same or are different in some way. Antonyms for nonidentical could include identical, same, alike, indistinguishable, and twin. These words refer to things that are the same, or almost the same, as each other. Other antonyms for nonidentical include identical, uniform, consistent, standardized, and perfect. These words suggest a level of sameness or consistency that is not present in things that are nonidentical. By using antonyms for nonidentical, it becomes easier to describe things that are different or the same, making it easier to communicate and understand ideas.