Largest libraries in the U.S. as of October 2012, by number of volumes held
* Definition of volume:
Academic libraries: A single unit of any printed, typewritten, handwritten, mimeographed, or processed work, distinguished from other units by a separate binding, encasement, portfolio, or other clear distinction, which has been cataloged, classified, and made ready for use, and which is typically the unit used to charge circulation transactions.
Public librariesHoldings are defined as the number of cataloged items. Include print materials, electronic books, audio materials, and video materials acquired as part of the collection and cataloged, whether purchased, leased, licensed, or donated as gifts.