accession

Accession is a term used across several fields to describe the act of joining, entering, or gaining possession, often through a formal process. The word originates from Latin accessio, meaning “an approaching,” and entered English via Old French. In general use, accession can refer to gaining a position, a right, or tangible property.

In international law and diplomacy, accession denotes the act by which a state becomes a party to a treaty after the treaty has already been opened for signature. The effect is typically the same as if the state had originally signed and ratified the treaty, but the procedures and dates of entry into force depend on the treaty’s terms. Accession is distinct from initial signature or ratification.

In governance and monarchy, accession commonly refers to the moment a person becomes sovereign or otherwise assumes the throne or a high office. It marks the onset of a reign or tenure and is often celebrated as a formal date of entry into the position.

In museums, libraries, and archives, accession is the formal process of recording an object as a permanent part of a collection. An accession number is a unique identifier assigned to the item, and an accession record documents provenance, date of acquisition, donor information, and cataloging data. Accessioning is the process of adding items to a collection, and it is typically followed by cataloging, conservation, and storage practices.

In scientific collections, accession numbers are used to track individual specimens or lots, ensuring stable provenance and traceability within the collection.