the action of taking possession of something, especially land (a region or territory), and adding it to one's own range, or the state of being thus possessed;
e.g. The Mexican-American war led to the American annexation of California.
(noun)
something, especially land (a region or territory) that has been taken possession of and added to a larger state or country;
e.g. This region is the country's annexation from the war.