Bibliographic item:

An item or set of items in any physical form, either serial or nonserial, published, issued or treated as an entity and, as such, forming the basis for a single bibliographic description.  The bibliographic item is the entity referred to by the item identifier.  Examples of bibliographic items are:  a one-volume book, a set of maps, a musical score with parts, a compact digital disc, a multimedia kit, a manuscript collection, a microform journal, a videotape with an accompanying pamphlet, a looseleaf publication together with its serially-issued updates.  See also holdings item.