Focus on the pronunciation of oath
› an official promise, especially when you promise to tell the truth in court: The witness took the oath. A psychologist cannot be compelled to attend a disciplinary hearing or to swear on oath.
on/under oath › LAW having officially promised to tell the truth in court: She was called to testify under oath before a congressional panel.
take the oath of office › GOVERNMENT to accept a job in a government, especially in the US, in a ceremony which requires you to make an official promise to serve your country: The newly-elected Democrat took the oath of office in the Senate yesterday and quickly introduced his first bill.