Deposition, in law, written testimony of a witness or some other person, taken under oath, for use in court. A deposition is in the form of answers to written or oral questions. Authority to take the deposition must come from the court. Depositions may be taken when witnesses cannot appear in court because of special circumstances, such as distance, illness, or age. Depositions are also used by each party in a case to obtain information from the other as part of a process called discovery.