To annex means to incorporate or add territory into an existing political unit, such as a country. It involves taking control over another area and making it part of your own.
Related terms
Expansionism: The belief or policy that a country should expand its territorial boundaries, often through military conquest or colonization.
Manifest Destiny: The idea prevalent in the 19th century that it was America's destiny to expand its territory across North America.
Treaty: An agreement between two or more nations that establishes peace, resolves disputes, or regulates trade.