The word "annex" refers to the addition of a territory or building to an existing one. Some synonyms for annex include "attachment," "addition," "extension," "adjunction," and "appendage." These terms are all similar in meaning, as each implies the idea of joining or adding something to something else. Other possible synonyms for annex might include "incorporation," "consolidation," "merger," or "union," which suggest a more complete and permanent joining of entities. Regardless of the specific word used, an annex typically refers to a space that is supplementary to, or integrated with, an existing structure or territory.