Witness (noun) – One with knowledge, as an observer or expert. A witness has information of use to legal officials who are examining the state of affairs in the world for some purpose. Witness, from old English, means a person with knowledge, and the kinds of knowledge the witness may have is as extensive as the scope of human understanding, limited only by the needs of a particular inquiry and the manner in which the knowledge was gained. Witnesses may exist who are unknown to legal officials, or they may be consulted informally.

Also see Defendant, and Victim.