Pronunciation: (ak-sesh'un),[key] —n. 1. the act of coming into the possession of a right, title, office, etc.: accession to the throne. 2. an increase by something added: an accession of territory. 3. something added: a list of accessions to the college library. 4. Law.addition to property by growth or improvement.
5. consent; agreement; approval: accession to a demand. 6. Internat. Law.formal acceptance of a treaty, international convention, or other agreement between states.
7. the act of coming near; approach.
8. an attack or onset, as of a disease.
—v.t. 1. to make a record of (a book, painting, etc.) in the order of acquisition.
2. to acquire (a book, painting, etc.), esp. for a permanent collection.