Definition of: accession

(ak·sesh′ən) noun
1. One who or that which is added; addition.
2. Attainment, as of office; succession to a throne; induction or elevation.
3. Access; admittance; approach: the accession of light.
4. Assent; agreement; consent.
5. Law The acquisition of property of a concomitant nature by virtue of the ownership of the principal, to which it is accessory as an incident.
6. A beginning, increase, or paroxysm, of disease, anger, folly, etc. See ACCESS.
— v.t. To record, as additions to a library or museum. [<L accessio, -onis <accedere.
See ACCEDE.]
—ac·ces′sion·al adjective Synonyms (noun): addition, arrival augmentation, enlargement, extension, inauguration, increase, influx. See ENTRANCE.