A written statement that someone makes after promising officially to tell the truth. An affidavit can be used as proof in a law court.Both copies will be required in court. An affidavit is a written statement made under oath that is typically used in legal proceedings. Learn their purpose, when to use, and how to write. An affidavit is a written declaration under oath, made without notice to the adverse party. An affidavit is a written statement that you swear is true and that may be used as evidence in a court of law. For all examinees requiring accommodations or supports, you should complete the Examinee. Affidavit and Accommodations Log found on the ACT-hosted webpage. This article lists direct English translations of common Latin phrases.