accession

noun

1. (countable, uncountable)A coming to; the act of acceding and becoming joined.

   “a king's accession to a confederacy”

2. (countable, uncountable)Increase by something added; that which is added; augmentation from without.

   “The only accession which the Roman empire received, during the first century of the Christian Aera, was the province of Britain.”

   “1803, John Browne Cutting, “A Succinct History of Jamaica” in Robert Charles Dallas, The History of the Maroons, London: Longman and Rees, Volume 1, p. xli, […] armed vessels being provided, their crews were soon recruited by accessions from the needy or adventurous, the discontented or the bold.”

3. (countable, uncountable)Increase by something added; that which is added; augmentation from without.
4. (countable, uncountable)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. (countable, uncountable)The act by which one power becomes party to engagements already in force between other powers.

   “accession to the European Union”

6. (countable, uncountable)The act of coming to or reaching a throne, an office, or dignity.

   “her accession to the throne”

   “This is the 6 ft. 4-6-0 engine No. 8301, Springbok, the second design produced by Mr. Edward Thompson since his accession to office as Chief Mechanical Engineer.”

   “Charles will be formally proclaimed King at a historic Accession Council in an ancient ceremony at St James’s Palace on Saturday, it has been announced.”

7. (countable, uncountable)The invasion, approach, or commencement of a disease; a fit or paroxysm.
8. (countable, uncountable)Agreement.
9. (countable, uncountable)Access; admittance.
10. (countable, uncountable)A group of plants of the same species collected at a single location, often held in genebanks.
11. (Scotland, countable, uncountable)Complicity, concurrence or assent in some action.

verb

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