Swear is the action of either administering or taking an oath.
Public officials are sworn in prior to taking their office. For example, inauguration day is when the President swears an oath of office. Witnesses taking the stand in court to testify must also swear that they will testify truthfully.
Judges generally administer oaths to individuals taking the oath. For example, the U.S. Supreme Court Chief Justice swears in the incoming President, and the presiding trial judge swears in testifying witnesses.
An example of a judge swearing in a witness could be the judge asking the witness, “you do solemnly swear that the evidence you shall give in the issue (or matter) now pending between _______ and _______ shall be the truth, the whole truth, and nothing but the truth, so help you God,” with the individual taking the oath responding (generally in the affirmative).
[Last updated in October of 2021 by the Wex Definitions Team]