Affidavit definition (noun)
An affidavit is a sworn statement of truth written or signed by an affiant, usually used in court proceedings as evidence. It is also known as a certificate of affirmation and is often referred to as an affidavit (the word “affidavit” is not always used).
Affidavits are considered the most formal type of legal document; they must be prepared by someone who has personal knowledge of the facts being stated.
The purpose of an affidavit is to state facts about matters that are within the personal knowledge of the affiant: for example, where the person was on the day before yesterday when it happened so there is no need to ask anyone else.
Affidavits were originally created to keep official records from being lost or destroyed because of paper loss after the invention of the printing press. Many states require affidavits to be made under oath either at trial or during other legal proceedings.