Chapter 1 - Purpose and Background
Before becoming a U.S. citizen, an eligible naturalization applicant must take an oath of renunciation and allegiance (Oath of Allegiance) in a public ceremony.  The applicant must establish that it is his or her intention, in good faith, to assume and discharge the obligations of the Oath of Allegiance.  The applicant must also establish that his or her attitude toward the Constitution and laws of the United States makes the applicant capable of fulfilling the obligations of the oath. 
During the naturalization interview, the applicant signs the naturalization application to acknowledge his or her willingness and ability to take the Oath of Allegiance and to accept certain obligations of United States citizenship. Under certain circumstances, an applicant may qualify for a modification or waiver of the oath.  In such cases, an officer draws a line through the designated modified portions of the oath and the applicant is not required to recite the deleted portions. 
Applicants must generally recite the Oath of Allegiance orally during a public ceremony. Merely signing the naturalization application and a copy of the oath does not make the applicant a U.S. citizen.
Pub. L. 106-448 (PDF) – Waiver of Oath of Renunciation and Allegiance for Naturalization of Aliens having Certain Disabilities Act of 2000