accession

UK: /ækˈsɛʃ^ən/ US: /ækˈsɛʃən/ ,(ak sesh′ən)

WordReference Random House Learner's Dictionary of American English © 2026

ac•ces•sion /ækˈsɛʃən/   n. [uncountable]

1. the act of taking up a high office or position:
   her accession to the throne of Russia.

See -cess-.

WordReference Random House Unabridged Dictionary of American English © 2026

ac•ces•sion  (ak sesh′ən), 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. Law [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. 

9. to make a record of (a book, painting, etc.) in the order of acquisition.
10. to acquire (a book, painting, etc.), esp. for a permanent collection.

• Latin accessiōn- (stem of accessiō) an approach, addition. See access, -ion
• 1580–90

ac•ces′sion•al, adj. 

Collins Concise English Dictionary © HarperCollins Publishers::

accession / əkˈsɛʃən/ noun

1. the act of entering upon or attaining to an office, right, condition, etc
2. an increase due to an addition
3. an addition, as to a collection
4. an addition to land or property by natural increase or improvement
5. the formal acceptance of a convention or treaty
6. agreement; consent
7. a less common word for access2

verb

1. (transitive) to make a record of (additions to a collection)

acˈcessional adjective