An annex is an extension of or an addition to a building. A small room off of a main room is an annex, and attics are another type of annex.

As a noun, an annex is part of a building or an addition to a main structure, or it can be an attachment, as in "an annex to the current plans." When used as a verb, the word means something a little different. Sometimes annex is used as a nice word for "take" or "grab," as when Nazi Germany took the Sudetenland from Czechoslovakia in 1938 and added it to their own territory. In order to annex something to what is yours, you have to take it away from someone else.

Definitions of annex

v attach to

Type of:
add on, affix, append, supplement
add to the very end

v take (territory) as if by conquest

“Hitler annexed Lithuania”
colonise, colonize
settle as a colony; of countries in the developing world
Type of:
arrogate, assume, seize, take over, usurp
seize and take control without authority and possibly with force; take as one's right or possession

n an addition that extends a main building

annexe, extension, wing
an extension at the end and at right angles to the main building
Type of:
add-on, addition, improver
a component that is added to something to improve it