The term 'Building Annex' can be broken down into two words: 'WING' and 'ELL'. WING is a four-letter word meaning an extension of a building, usually at a right angle to the main structure. An ELL is a three-letter word meaning an extension of a building, usually at a right angle to the main structure, but with a curved shape. Together, these two words form the term 'Building Annex', which refers to an additional structure attached to a main building.