What is the USCIS N-400?

Answer 1

The N-400 is the form used by residents to apply online or by mail for US citizenship. Depending on your case, there are additional forms to fill out for payment of fees and to apply for fee waivers in some cases.

Answer 2

USCIS stands for U.S. Citizenship and Immigration Services. N-400 is the application you need to submit to USCIS to apply for citizenship

Answer 3

U.S.C.I.S. is an acronym that stands for "United States Citizenship and Immigration Services." N-400 is the application that one fills out if she or he wants to apply to become a naturalized United States citizen. "Naturalized" is the way one can become a United States citizen if she or he was not born on United States soil/land. There are prerequisites and additional steps one most complete and succeed in to be considered to take the Oath of Allegiance to the United States of America.