n. Something appended or added; an adjunct, concomitant, appendage, or accessory.n. Specifically— An addition appended to a document or book relating to the main work, usually consisting of explanatory or statistical matter adding to its value, but not essential to its completeness, and thus differing from a supplement, which properly is intended to supply deficiencies and correct inaccuracies.n. In anatomy, a process, prolongation, or projection. See the phrases following.To add as an appendix.