An affidavit is a sworn statement of fact that can be used in a variety of legal proceedings, from bankruptcy cases to family and civil litigation matters. An affidavit is a written statement that you swear is true and that may be used as evidence in a court of law.AFFIANT - A person who makes and signs an affidavit. An affidavit is a written statement, sworn to be true, that can be used as evidence in legal proceedings. Learn more in our legal dictionary. An affidavit is a self-serving declaration used in legal service. Consider it sort of like a confession, or a witness statement.