nonidentical

Nonidentical is an adjective used to indicate that two or more things are not identical; in other words, they are not the same object or do not share all the same properties in a way that would treat them as identical. The word is widely used in everyday language as well as in specialized contexts to mark difference, individuality, or inequality between items, people, or data.

In mathematics and logic, the concept of identity describes when two objects are the same in a formal sense. Nonidentical, by contrast, emphasizes that two elements are distinct or not the same object, even if they may share some properties. In practice, writers often substitute terms such as distinct or different, since those more directly convey inequality without invoking the formal notion of identity.

In biology, nonidentical twins refer to fraternal twins, which develop from two separate eggs fertilized by two separate sperm. They are genetically more diverse than identical twins, who arise from a single fertilized egg that splits. The term highlights the lack of complete genetic sameness, though nonidentical twins can still share a significant portion of their DNA.

Hyphenation varies by style guide; nonidentical is commonly written as one word, while some guides prefer non-identical when used before a noun. In general usage, nonidentical serves as a concise way to contrast with identical or to assert that two entities are not the same.