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 in which the signer or "affiant" verifies that the document is true.An affidavit is a sworn written statement used as evidence in court, stating facts under oath, but cannot be crossexamined. In a nutshell, an affidavit is a sworn statement that is documented in writing. They are written plainly, for an audience with no legal experience, and are easy to understand. The Legal Definition of an Affidavit. You may be able to use a Small Estate Affidavit to have the property transferred to you. An affidavit is a written statement made under oath or affirmation. It's used as evidence in legal proceedings.