accession

Short definition from Wiktionary

Noun

1. 1
   A coming to; the act of acceding and becoming joined.
2. 2
   Increase by something added; that which is added; augmentation from without.
3. 3
   Increase by something added; that which is added; augmentation from without: Such augmentation that adds to the collections of a museum or archive; a thing thus added.
4. 4
   A mode of acquiring property, by which the owner of a corporeal substance which receives an addition by growth, or by labor, has a right to the part or thing added, or the improvement (provided the thing is not changed into a different species).
5. 5
   The act by which one power becomes party to engagements already in force between other powers.
6. 6
   The act of coming to or reaching a throne, an office, or dignity.
7. 7
   The invasion, approach, or commencement of a disease; a fit or paroxysm.
8. 8
   Agreement.
9. 9
   Access; admittance.
10. 10
    A group of plants of the same species collected at a single location, often held in genebanks.
11. 11
    Complicity, concurrence or assent in some action.

Verb

1. 1
   To make a record of (additions to a collection); to add (something) to a collection (usually a museum's or archive's collection).