annex

Concise Oxford English Dictionary © 2008 Oxford University Press:
annex

▶verb /əˈnɛks/ 

• 1 add as an extra or subordinate part.

• 2 add (territory) to one's own territory by appropriation.

▶noun /ˈanɛks/ (chiefly Brit. also annexe) (pl. annexes)

• 1 a building joined to or associated with a main building.

• 2 an addition to a document.

– derivatives
annexation noun,
annexationist noun & adjective.

– origin ME: from OFr. annexer, from L. annectere ‘connect’.