An affidavit is a written statement which you swear is true and which may be used as evidence in a court of law. An affidavit is a written statement that you swear is true and that may be used as evidence in a court of law.A written declaration upon oath made before an authorized official. 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. There is one meaning in OED's entry for the noun affidavit. A sworn written statement of evidence used mainly to support certain applications and, in some circumstances, as evidence in court proceedings. Learn how to use and draft affidavit forms with this comprehensive guide. Affidavit refers to a written promise, and its Latin roots connect it to another kind of promise in English.