The following is excerpted with permission of the author from Jean Peters, ed. This chapter is concerned primarily with descriptive bibliography, especially with the terms that the book collector must master before he or she can use descriptive bibliographies intelligently and read booksellers' catalogues wisely. For this purpose, we need to sharpen the definition of such a common word as edition .
Publishers tend to use the word rather loosely, but edition has a precise bibliographical meaning.
An edition of a book is all copies printed at one or later times from the same setting of type . Within an edition, all copies printed at any one time are called an impression . A number of impressions from the same setting of type may be produced over a period of many years, but they are all part of the same edition, because the type itself is identical in each of these impressions. In 1866, for instance, Thomas MacKellar wrote and published a manual of typography called The American Printer . He had electrotype plates made from the original setting of type, and over the next dozen years or so, he issued nine further impressions of The American Printer , making only the occasional minor correction between one impression and the next.