appendage

An adjunct (something joined to) constitutes no real part of the thing or system to which it is joined, tho perhaps a valuable addition; an appendage is commonly a real, tho not an essential or necessary part of that with which it is connected; an appurtenance belongs subordinately to something by which it is employed, especially as an instrument to accomplish some purpose. A horse's tail is at once an ornamental appendage and a useful appurtenance; we could not call it an adjunct, tho we might use that word of his iron shoes. An attachment in machinery is some mechanism that can be brought into optional connection with the principal movement; a hemmer is a valuable attachment of a sewing-machine. An extension, as of a railroad or of a franchise, carries out further something already existing. We add an appendix to a book, to contain names, dates, lists, etc., which would encumber the text; we add a supplement to supply omissions, as, for instance, to bring it up to date. An appendix may be called an addendum; but addendum may be used of a brief note, which would not be dignified by the name of appendix; such notes are often grouped as addenda. An addition might be matter interwoven in the body of the work, an index, plates, editorial notes, etc., which might be valuable additions, but not within the meaning of appendix or supplement. Compare accessory; auxiliary.