English Reference
noun · verb

accession

n. · v.
US /əkˈsɛʃən/ UK /ɐksˈɛʃən/ ac·ces·sion UK spelling accession's, accession's, accessioned, accessioning

  1. 01 C1 Advanced Formal

    n.the moment someone officially becomes a king, queen, or leader.

    n.the formal act of attaining a position of high rank, such as a throne or a supreme office.

    Simple

    The country celebrated the 50th anniversary of the Queen's accession to the throne.

    In context

    Historians often debate whether his accession to the leadership was a result of popular support or clever political maneuvering.

    Usage

    Often followed by the preposition 'to'.

  2. 02 C1 Advanced FormalTechnical Law

    n.the act of a country or group joining an international agreement or organization.

    n.the formal process by which a state or power becomes a party to an existing treaty or international body.

    Simple

    The government is preparing the final documents for the country's accession to the European Union.

    In context

    The treaty's accession clause allows any sovereign state to join provided they meet the specific economic and human rights criteria.

    Usage

    Commonly used in the context of international law and diplomacy.

  3. 03 C2 Proficiency FormalTechnical

    n.a new item that is added to a library, museum, or gallery.

    n.an object or group of objects added to a permanent collection, such as in a museum or archive.

    Simple

    The museum's latest accession is a rare painting from the 17th century.

    In context

    The library staff spent weeks cataloging the new accessions received from the private estate of the late professor.

    Teacher's tip

    In museum contexts, the opposite process of removing an item is called 'deaccessioning'.

    deaccession
  4. 04 C2 Proficiency TechnicalArchaic Medicine

    n.the start of a sudden illness or a medical attack.

    n.the onset or commencement of a disease, or a sudden fit or paroxysm.

    Simple

    The patient suffered a sudden accession of fever during the night.

    In context

    The physician noted a rapid accession of symptoms that suggested the infection was spreading faster than anticipated.

    Teacher's tip

    This sense is rare in modern general English and is mostly found in older medical texts.

  5. 05 C2 Proficiency Technical

    v.to record a new item in a museum or library's official list.

    v.to officially record an addition to a collection, typically assigning it a unique identification number.

    Simple

    The archive needs to accession these old letters before they can be studied.

    In context

    The curator must accession every artifact immediately upon arrival to ensure the legal chain of custody is maintained.

The ministry described the coalition as “an open international coalition that welcomes the accession of all countries that align with its goals and principles”, adding that it continues to receive new membership applications.

Al Jazeera· 14 Aug 2026

We will move forward with Ukraine’s EU accession process.

The Guardian· 24 Aug 2026

Ultimately from Latin accessiō(n), from accēdō (English accede). Cognate to French accession. First attested in 1646.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Latin accessiō
Level C1 · Advanced
Frequency Frequent
Updated