U.S. Citizenship is obtained either by birth, derivation, or naturalization.  U.S. citizens may live and work in the U.S. permanently, and can’t lose this status by extended travel abroad, in contrast to Permanent Residence (“Green Card”) status.  U.S. citizens may petition for the permanent resident status of their parents, spouses, children and siblings.
 
       Requirements
 

• Generally, 5 years in permanent resident status (three years may be sufficient for those married to U.S. citizens).

• Generally, physical presence, continuity of residence, and good moral character standards.

• Satisfactory exam results in U.S. government, history, and civics as well as the ability to speak, read, and write English.  In certain cases, exceptions may be granted to the testing requirements based on age and duration of permanent residency, as well as medical limitations.