An Accession number is a unique identifier given to a DNA or protein sequence when it is submitted to a sequence database (such as UniProt, GenBank, EMBL, DDBJ , etc.). The initial deposition of a sequence record is typically referred to as version 1. If the sequence is updated, the version number is incremented, while the accession number remains constant.
The term accession number is also used to describe the sequential number given to each new book, magazine subscription, or recording as it is entered in the catalog of a library. If an item is removed from the collection, its number is usually not reused for new items. This numbering system is usually in addition to the library classification number (or alphanumeric code) and to the ISBN or International Standard Book Number assigned by publishers.
