swear in
To administer an oath to someone as part of the official process of taking public office. A noun or pronoun can be used between "swear" and "in." The current president was sworn in after his predecessor died of a sudden heart attack. We will swear you in as newly qualified members of the police force at the end of the ceremony.
swear someone in (as something)
to administer an oath to someone who then officially begins in office. The judge swore Alice in as street commissioner. The judge swore in Alice as the new director.
swear in
Administer a legal or official oath to, as in The new mayor will be sworn in tomorrow. [c. 1700]
swear in
v. To administer a legal or official oath to someone: The police department swore in 15 new officers. The Chief Justice will swear the new President in.