"Non est factum" is a Latin phrase that translates to "it is not his/her deed" in English. It is a legal term used to describe a situation where someone signed a contract under a mistaken belief about its nature or content. Synonyms for "non est factum" include "mistake of fact", "untrue in fact" or "misrepresentation of fact". These synonyms highlight the underlying concept of the phrase, which refers to a false impression that led to the signing of a document without full understanding or consent. Understanding these synonyms can help legal professionals navigate contracts or agreements where the concept of "non est factum" may be applicable.