What does N-400 stand for?
Answer
Application for Naturalization
Explanation
N-400 stands for Application for Naturalization. The form number is part of the U.S. Citizenship and Immigration Services (USCIS) form numbering system, in which letters identify the form's general category and numbers identify the specific form: forms beginning with N relate to naturalization and citizenship under chapter 14 of the Immigration and Nationality Act, and Form N-400 is the principal application a lawful permanent resident files to apply for U.S. citizenship.
Other N-series forms include the N-336 (Request for a Hearing on a Decision in Naturalization Proceedings), the N-470 (Application to Preserve Residence for Naturalization Purposes for permanent residents working abroad in qualifying employment), the N-565 (Application for Replacement Naturalization or Citizenship Document), the N-600 (Application for Certificate of Citizenship for individuals who already are citizens by birth or derivation and need a certificate as proof), the N-600K (Application for Citizenship and Issuance of Certificate Under Section 322 for children of U.S. citizens residing abroad), and the N-648 (Medical Certification for Disability Exceptions, used to request a waiver of the English and civics requirements for medical reasons).
The Form N-400 is published in English only (USCIS does not produce translated versions, although some private organizations have translated guides), is 20 pages long in its current edition, and is divided into 18 parts covering the applicant's biographical information, residence and employment history, marital and parental history, time outside the United States, military service, criminal history, allegiance and good moral character questions, English and civics test eligibility, and requests for accommodations.
The N-400 was first introduced under the current numbering system in 1991 to replace the older Form N-405 (Application to File Petition for Naturalization). It has been revised numerous times since, most recently in April 2024 to incorporate the current fee structure and to streamline portions of the form. The application is governed by sections 310 through 348 of the Immigration and Nationality Act (Title III, Chapter 2 of the Act, codified at 8 U.S.C. sections 1421 through 1459), which set out the substantive and procedural requirements for naturalization.
Why this matters for your test
Knowing what N-400 stands for connects the form number to its legal purpose: an application for naturalization, the only path to U. S. citizenship for most adult immigrants.
It also distinguishes the N-400 from the related N-series forms that handle hearings, certificates, and special exceptions, all of which an applicant or their family may encounter.
Source: USCIS Application Guide (2025)
